CHAPTER VIII.

It is exceedingly desirable, in a practical point of view, to understand the precise character of the reciprocal action which takes place between the earth and the counter-trade, and produces the varied phenomena which mark our climate. We have seen that the same laws, other things being equal, operate every where, and that analogies may be sought in the character of those phenomena elsewhere, under the same, or different, modifying circumstances. Looking, therefore, at the magneto-electric movable machinery as a whole, and its influence upon the atmospheric circulation and conditions, we find many facts which point to a primary action in the counter-trade, and others that point as significantly to a primary local-inducing-action in the earth. Let us briefly review those to which we have alluded, and advert to some others, and see what solution of the question they will justify:

The belt of inter-tropical rains appears to be, in width, and amount of precipitation, and annual travel north and south, proportionate to the volume of trades which blow into it, the quantity of moisture they contain, and the elevation of the surface over which they meet.

South America is the most thoroughly-watered country within the tropics, except, perhaps, portions of Hindoostan, Burmah, Siam, etc., on south-eastern Asia. The contrast between both, and Africa, as far as explored, and as shown by its rivers, is most obvious. The Amazon, alone, delivers more water to the ocean than all the rivers of Africa.

Of the width of the belt of rains over Africa, in the interior, we know little. Its northern extension is less, by from 7 deg. to 10 deg., than the same belt over South America, the West Indies, and Mexico. Probably its southern is also. Upon South America, the southern edge is carried down to Cochabamba, in latitude 18 deg., and probably to 25 deg., to the northern edge of the coast-desert of Peru, while it is rarely, if ever, found over the Atlantic below 7 deg., a difference of 12 deg. to 20 deg.. Over South America, too, the quantity of water which falls is also vastly in excess of that which falls upon the Atlantic. The main cause of these differences is obvious. The N. E. counter-trades which blow over Africa, originate on a surface which is rainless, as eastern Sahara, Egypt, Arabia, etc., or subject to a dry season by the northern ascent of the southern line of the extra-tropical belt, as the Barbary States, Syria, Persia, etc., and their supply of moisture is necessarily scanty. On the south, the S. E. trades originate, in part, upon the eastern portion of southern Africa, and, in part, upon the Indian Ocean, and from the latter source, and a portion of the Mediterranean, doubtless most of the water which falls upon Central Africa, is derived.

The N. E. and S. E. trades which blow into the inter-tropical belt upon the eastern portion of the Atlantic, originate upon similar surfaces, and with like effect. Thus, the S. E. trades, in summer, are from the Southern portion of Africa, and the N. E., in part, from the Mediterranean; and, in winter, the N. E. from the deserts, Senegambia, Nigritia, etc., and the S. E., owing to the narrowing of the African continent, mainly from the South Atlantic and Indian Oceans. Going west, the belt widens, and its range increases until the Andes are reached; but under their lee, on the western side, a totally different state of things is found, and the belt of the coast becomes broken and irregular, as we have seen in the citation from Maury.

The width, extension, and excessive precipitation of the belt, over South America, follow the same law. The South Atlantic widens out by the trending of the coast to the S. W., and furnishes a large area for the unobstructed formation and evaporative action of the S. E. trades. So the trending of the coast to the N. W., from 5 deg. south to the northward, opens a large area for a like formation and action of the N. E. trades. No correspondingly favorable circumstances exist any where, except, perhaps, around Hindoostan, and there the fall of rain is very excessive in some places, as on the Kassaya hills, to the extent of 400 inches per annum. In addition to this, the magnetic line of no variation, and of greater intensity, which runs from our magnetic pole, obliquely, S. S. E., to its opposite and corresponding pole in the southern hemisphere, enters the Atlantic on the coast of North Carolina, and traverses it, and the eastern portion of South America, through the whole trade-wind region. The table-lands, and slopes, and high mountain peaks, meet the trades successively, as they go west, and the latter wrench from them, to an unusual extent, their moisture; depressing the line of perpetual snow, by an increase of quantity on the eastern sides, several thousand feet, as it is for a like cause depressed on the southern side of the Himmalayas. On the eastern slopes and tops of the Andes, as we have seen, and owing to their elevation, falls the moisture which, according to the working of the machinery, and the law of curvature, should bless the coast line of Peru and northern Chili, the eastern Pacific, northern Mexico, California, Utah, and New Mexico; and, while the Andes stand, the curse of comparative aridity must rest upon them all.

Southern Chili, and western Patagonia are supplied by the N. E. trades, which originate in the West Indies, the Gulf of Mexico, and the Caribbean Sea, and the Pacific, off Central America, in the neighborhood of the Bay of Panama. But there, again, the same effect of elevation is seen. The mountain slopes of southern Chili and Patagonia are abundantly supplied, and their mountain ranges are drenched with rain, while eastern Patagonia and southern Buenos Ayres, under their lee, are comparatively dry. So the S. E. trades, which originate off the western coast of South America, curve in upon, and aided by the oceanic currents, supply, abundantly, the N. W. coast of this continent, north of California; and there, too, the coast, and its elevated ranges, receive, as we have seen, a very large proportionate supply of their moisture. Substantially, the same state of things, as far as circumstances permit, is reproduced upon Malaysia, Hindoostan, etc., and the interposition of arid New Holland upon the evaporating trade-surface may be distinctly traced upon south-western Asia. Deserts abound there; the Caspian Sea receives the drainage of a very large surface, without an outlet; their southern line of extra-tropical rains is carried up very far in summer, and their dry season is intensely hot. (See an article in the American Journal of Science, for July, 1846, by Azariah Smith.)

Another fact in this connection is worthy of a moment's consideration. The magnetic equator, as sought by the dipping needle, is not coincident with the geographical one. Humboldt found it, on the Andes, at 7 deg. 1' south, and it has been found still lower in the Atlantic. Over Africa it rises above the geographical equator, and descends again on the Indian Ocean. About midway the Pacific, it becomes coincident with the equator of the earth again. (See diagram, on page 83.) Perhaps it is not known, with certainty, why this is so. The south pole may be situated nearer the geographical pole than the north one--but this is not believed to be so, nor could it make the difference. The greatest southern depression of the magnetic equator is found where the lines of greatest intensity, and of no variation, are found; and at the more intense of these lines exists the greatest depression. From this, I think, it may be inferred that the needle is affected by the greater magnetic intensity of the northern hemisphere, to which it may yet appear the obliquity of the earth's axis is owing. However this may be, or whatever the cause, no marked effect is produced upon the trades. The S. E. trades, by reason of the greater extent of ocean-surface on which they originate, are every where the most extensive, regular, and forcible. The south polar waters, from which they rise, are every where trenching upon, and overriding, the north polar ones; and thus, by a most beneficent provision, the greater portion of the habitable surface is placed in the northern hemisphere, and the principal portion of the southern is left open to an extensive, active evaporative action, which supplies the northern habitable surface with a large excess of the needed moisture.

The condensation, and consequent precipitation, which takes place at the passing of the trades, as we have already said, over the ocean and lowlands, takes place mainly in the day-time. Upon the table-lands and mountain-ranges, it often continues during the evening and night. The morning, and early part of the day, however, in tropical countries, are generally fair at all elevations.

Storms also originate in the equatorial belt, and issuing forth in great volume and with great intensity of action, find their way up even within the Arctic circle. Those which pass over this continent, or the northern Atlantic, generally originate in the West Indies, some of them over the Caribbean Sea, some over the islands, and some over the open ocean to the east of them; and, nearly all the most violent, during the months of August, September, and October. It would seem most probable that the primary action in such cases was in the trades themselves, but it is by no means certain that such is the case. This is the class of storms of which Mr. Redfield has industriously investigated some twenty or more; Mr. Espy some, and Lieutenant Porter two. Their course, when very violent, is often more directly north than that of storms, however violent, which originate north of the calms of Cancer, owing, perhaps, to their greater paramagnetic character. This course I have myself observed, in several instances, about the period of the autumnal equinox--never, however, more southerly than from S. W. to N. E., on the parallel of 41 deg., except in three, and, perhaps, four, instances, when it has been S. W. by S. to N. E. by N. I know of no class of storms in relation to which the evidence of primary action in the counter-trade is stronger than in those of the class which originate on the ocean east of the Windward Islands. But it is not satisfactory as to them. Doubtless the conflict of polarities between the passing trades is sufficient to produce the showers and rains which are ordinarily found over the ocean and lowlands, in the equatorial belt; but it is doubtful whether it is sufficient to produce such extensive, long-continued, and violent action, as that which characterizes the hurricane autumnal gales.

They occur, too, at the time when the whole machinery of distribution has reversed its course, and is rapidly pursuing its journey south. It is a period of great magnetic disturbance, over both land and sea; of more active gales and local-increased precipitation. At the Magnetic Observatory of Toronto, Canada West, these disturbances are carefully and systematically observed, and their maxima, or periods of greatest disturbance occur in April and September. (See Silliman's Journal, new series, vol. xvii. p. 145.)

The tendency to volcanic action is not as great at the autumnal, as at the vernal equinox, for the reason that most of the volcanic action of the western hemisphere develops itself now upon South rather than North America. But both exist, and are active, and what are improperly termed equinoctial storms, and gales, and rains, are proverbial during, or just subsequent to, both periods with us--as they are when the same change, called the breaking up of the monsoons, takes place in the line of magnetic intensity, over southern and eastern Asia. A volume might be filled with extracts, showing, at least, most remarkable coincidences between violent volcanic action and great atmospheric disturbance. Perhaps the increased fall of rain at and after the equinoxes, in the northern hemisphere, and in certain localities subject to volcanic activity, is as strikingly illustrated by the register, kept by Mr. Johnson, on the volcanic Island of Kauai, one of the Hawaiian group, already alluded to, as in any other case, although it is by no means a singular one. The greatest fall of rain, in any month except April and October, was eight inches. In April, the fall was fourteen inches, in October, eighteen inches. Neither the equatorial, nor extra-tropical belt, were over the island during those months; but they were the N. E. trades, and the result was owing solely to the interposition of high volcanic mountains, in a state of disturbance, into, or near, the strata of the counter-trade. Mr. Dobson, in stating a theory to which we shall hereafter advert, advances the following proposition:

"7. Cyclones (hurricanes) begin in the immediate neighborhood of active volcanoes. The Mauritius cyclones begin near Java; the West Indian, near the volcanic series of the Caribbean Islands; those of the Bay of Bengal, near the volcanic islands on its eastern shores; the typhoons of the China Sea, near the Philippine Islands, etc."

The peculiar stormy state of the atmosphere, over the Gulf Stream, to which I have alluded, certainly affords no evidence of primary atmospheric action. It is a body of south polar water, pursuing its way under the guidance of magnetism--maintaining its polarity--arched somewhat like the roof of a house, by the outward pressure of a cold north polar current which it has met to the east of the Banks of Newfoundland, and forced to take an in-shore course to the southward, and the bodies of water which the rivers discharge, and a conflict with the north polar surface-winds which sweep over it, and fogs, and thunder, and rain, are a matter of course. Dr. Kane met a portion of this singular current in Baffin's Bay, north of 75 deg., which had preserved its characteristics and a considerable proportionate excess of heat, although it probably had been around Greenland, or found its way to the west, toward the magnetic pole, through some of its northern fiords or straits. (Grinnel Expedition, p. 120.)

The investigations of Lieutenant Maury show, that when the Gulf Stream turns to the eastward, crossing the lines of declination at right angles, as the counter-trades also seem to do in the same latitude, it is carried up, in summer, several degrees to the north, and descends again in winter--thus demonstrating its connection with the shifting magnetic machinery which controls alike the ocean, the atmosphere, and the temperature of the earth.

There are other irregularities which deserve to be noticed, in this connection, although the analogical evidence they afford is far from being decisive.

I have already said that it was within my own observation, that alternating lines of heat and cold, as well as rain and drought, existed frequently, without regard to latitude, following, to some extent, the course of the counter-trade. Such lines have been observed by others.

Thus, Mr. Espy, after describing a snow-storm, which was followed by a very cold N. W. wind, of several days' continuance, says:

"This cold air covered the whole country, from Michigan to the eastern coast of the United States, till the beginning of the great storm of the 26th January; and, what is worthy of particular notice is, that the temperature began to increase first in the north and north-west. On the morning of the 25th, in the north-western parts of Pennsylvania, and northern parts of New York, the thermometer had already risen in some places 30 deg., and, in others, above 40 deg.. While in the S. E. corner of Pennsylvania, and in the S. E. corner of New York it had not begun to rise. The wind also began to change from the north-west to south and south-east, first in the north-west parts of Pennsylvania and New York, some time before it commenced in the south-east of those States; and, during the whole of the 25th, the thermometer, in the north of New York, continued to rise, though the wind was blowing from the southward, where the thermometer was many degrees lower."

Thus, too, Mr. Redfield (American Journal of Science, November, 1846, p. 329):

"On the contrary, in times of the greatest depression of the thermometer, in numerous instances, the cold period has been found to have first taken effect in, or near, the tropical latitudes, and the Gulf of Mexico, and has thence been propagated toward the eastern portions of the United States, in a manner corresponding to the observed progression of storms."

This was because the cold N. W. wind which followed storms began to follow them as the storms curved and passed to the N. E.

They occur in Europe also. Says Kaemtz:

"Such contrasts are not uncommon in Europe, and, in this respect, the Alps form a remarkable limit; for they separate the climates of the north of Europe from the Mediterranean climates, where the distribution of rain is not the same as in the center of Europe. Hence the differences between the climates of the north and south of France. If the winter is mild in the north, the newspapers are filled with the lamentations of the Italians and Provencals at the severity of the cold."

These facts seem to indicate a primary action in the counter-trade. Probably in connection with one class of storms they do, and with another do not. I shall endeavor to show the distinction when I come to the classification of storms.

The difference of seasons in this country, and over the entire northern hemisphere, is often very great. In a remarkable work of a remarkable man--"A Brief History of Epidemic and Pestilential Diseases," by Noah Webster, published in 1799, 2 vols.--a history of the weather for about two centuries--1600 to 1799 inclusive, is given generally, and then in a tabular form. Those who think that every considerable extreme which occurs exceeds any thing before known, will do well to consult that work. Droughts are described, where "there was not a drop of rain for three or four months, and cattle were fed upon the leaves of the trees." Winters, so intensely cold that the thermometer fell to 20 deg. below zero, at Brandywine; or so mild that there was little frost, and people upon Connecticut River plowed their fields, and the peach trees blossomed in Pennsylvania in February. These extremes generally existed in Europe and America at the same time, but occasionally they were opposite and alternate. Says Mr. Webster, in summing up the facts (vol. ii. p. 12): "It is to be observed that in some cases a severe winter extends to both hemispheres, sometimes to one only, and in a few cases to a part of a hemisphere only. Thus in 1607-8, 1683-4, 1762-3, 1766-7, 1779-80, 1783-4, the severity extended to both hemispheres. In 1640-41, 1739-40, and in other instances, the severe winter in Europe preceded, by one year, a similar winter in America. In a few instances, severe frost takes place in one hemisphere during a series of mild winters in the others; but this is less common. In general, the severity happens in both hemispheres at once, or in two winters, in immediate succession; and, as far as this evidence has yet appeared, this severity is closely attendant on volcanic discharges, with very few exceptions."

It will be seen that Dr. Webster (LL.D. and not M.D., and therefore the remarkable character of the work) attributes great influence to earthquakes and volcanic action. Probably he is correct in this. The present active volcanic action of the western hemisphere is nearly all within the trade-wind region, from Mexico to Peru inclusive. The West India islands are of volcanic origin, and the influence of volcanic action is not confined to a concussion of the earth, or the eruption of mud and lava. Its connection with magnetic action, and disturbance, is unquestionable. But whether they operate to increase or diminish the trades, and the extent to which they induce violent electric action and storms within and without the tropics, is a question which further observation must determine. The ripples of the ocean, compared by Lieutenant Banvard to that of a "boiling cauldron, or such as is formed by water being forced from under the gate of a mill-pond," are met with in the vicinity of volcanic islands, where hurricanes and water-spouts originate, and have been observed to precede storms, and be connected with a falling barometer. But whether they are volcanic or magneto-electric, it is difficult to determine. Dr. Webster remarks, as the result of observation, during the 17th century, that earthquakes had a N. W. and S. E. progression in the United States, and especially in New England. In a recent article, Professor Dana has examined, with great ability, the general and remarkable trending of coast lines, groups of islands, and ranges of mountains, from N. E. to S. W. and from N. W. to S. E. (American Journal of Science, May, 1847.)

The line of magnetic intensity, which connects our magnetic pole with its opposite, is now upon this continent nearly a N. W. and S. E. line, and the pole is fast traveling to the west. It may, and probably will yet, be established, that there is an intimate connection between the cause of volcanic action within the earth, to which the upheaval of the N. W. and S. E., and N. E. and S. W. ranges were due, and of magnetic action without, and between both, and the cause of the S. E. extension of our summer storms and belts of showers and barometric waves, and the peculiar N. W. wind. Our limits do not permit us to pursue the subject.

Much influence upon the weather has been attributed to the spots upon the sun. These spots are supposed to be breaks or openings in the luminous atmosphere or photosphere of the sun, through which its dark nucleus body is seen. Counselor Schwabe, of Dessau, has made them his study since 1826, and has arrived at some singular results. They seem to be numerous--in groups--and to appear periodically with minima and maxima of ten years. As the result of his observations, from 1826 to 1850, he gives us the following table and remarks:

+-----------------------------------------------+ | Year. | Groups. | Days showing | Days of | | | | no spots. | Observation. | |-------|---------|--------------|--------------| | 1826 | 118 | 22 | 277 | | 1827 | 161 | 2 | 273 | | 1828 | 225 | 0 | 282 | | 1829 | 199 | 0 | 244 | | 1830 | 190 | 1 | 217 | | 1831 | 149 | 3 | 239 | | 1832 | 84 | 49 | 270 | | 1833 | 33 | 139 | 267 | | 1834 | 51 | 120 | 273 | | 1835 | 173 | 18 | 244 | | 1836 | 272 | 0 | 200 | | 1837 | 333 | 0 | 168 | | 1838 | 282 | 0 | 202 | | 1839 | 162 | 0 | 205 | | 1840 | 152 | 3 | 263 | | 1841 | 102 | 15 | 283 | | 1842 | 68 | 64 | 307 | | 1843 | 34 | 149 | 312 | | 1844 | 52 | 111 | 321 | | 1845 | 114 | 29 | 332 | | 1846 | 157 | 1 | 314 | | 1847 | 257 | 0 | 276 | | 1848 | 330 | 0 | 278 | | 1849 | 238 | 0 | 285 | | 1850 | 186 | 2 | 308 | +-----------------------------------------------+

"I observed large spots, visible to the naked eye, in almost all the years not characterized by the minimum; the largest appeared in 1828, 1829, 1831, 1836, 1837, 1838, 1839, 1847, 1848. I regard all spots, whose diameter exceeds 50", as large, and it is only when of such a size that they begin to be visible to even the keenest unaided sight.

"The spots are, undoubtedly, closely connected with the formation of faculae, for I have often observed faculae, or narben, formed at the same points from whence the spots had disappeared, while new solar spots were also developed within the faculae. Every spot is surrounded by a more or less bright, luminous cloud. I do not think that the spots exert any influence on the annual temperature. I register the height of the barometer and thermometer three times in the course of each day, but the annual mean numbers deduced from their observations have not hitherto indicated any appreciable connection between the temperature and the number of the spots. Nor, indeed, would any importance be due to the apparent indication of such a connection in individual cases, unless the results were found to correspond with others derived from many different parts of the earth. If the solar spots exert any slight influence on our atmosphere, my tables would, perhaps, rather tend to show that the years which exhibit a larger number of spots had a smaller number of fine days than those exhibiting few spots."

These observations seem to show that the spots exert no influence upon the weather, and to be satisfactory. But, perhaps, they are not entirely so. No effect would, of course, be expected from day to day, and perhaps the annual mean may not be seriously disturbed, and yet the spots may seriously affect the seasons. Popular tradition has fixed upon certain periods, of 10, 20, and 40 years, for the return of winters of unusual severity; and the tables of Mr. Webster, and other facts, show that it is not wholly without foundation. If we, and those we have cited, are not mistaken in most of the views expressed, the natural effect of a partial interception or failure of the sun's rays, by or from the existence of the spots, would be to decrease the exciting power of the solar rays upon terrestrial magnetism, and, as a consequence, the volume of the trades and their amount of moisture. This would increase the mean heat of the summer in the temperate zone--for the less the volume of trade, the less precipitation and variable wind, and succeeding polar waves of cooler air, and the greater mean heat. On the other hand, the same cause, and the feebler heating power of the sun's rays, would make the winters more severe, both from an absence of a portion of heat, derived directly from the sun's rays, and a less mitigating influence, from the action of the trade, by reason of its decreased volume. So, too, the absence of spots, and a more powerful influence from the solar rays, may gradually carry the machinery further north in summer, and further south in winter, and thus make the seasons extreme without seriously disturbing the mean of the year. And both these may occur in a more marked degree over our intense magnetic area than in Europe. I am satisfied that they do so occur. That the partial failure of the sun's rays limits the transit of the machinery, and the volume of the trades during the latter half of the decade, and extends the transit and increases the volume during the first half, producing an occasional severe summer drought and severe winter, in the warmest portion of the decade. And that the variations correspond with the difference in the character and number of the spots in different decades, and hence the longer and shorter periods.

Turning to the tables of Dr. Webster, we find that a general tendency to extreme seasons does seem to exist from the 6th to the 10th year of every decade, and especially of every alternate decade. The periods of 1707-8, 1728, 1737 and 1739, 1749-50, 1758-9, 1779-80, 1798-9, are those in which the tendency was seen most decided. These tables are very general. The thermometer was not perfected till about 1700, and did not get into general use before 1750. There were very few meteorological registers kept, or accessible to Dr. Webster. Hence he was obliged to resort to such other sources of information as were open to him, and such statements as he found are not always entirely reliable. The oldest inhabitant is apt to express himself very strongly respecting present extremes, and fail somewhat in his recollection of those which have past. Still his tables afford general and obvious evidence of the regularity of those periodic conditions.

+---------------------------------------------------------+ |A. D.| Summer. | Winter. | |-----|-------------------------|-------------------------| | 1701| hot and dry | .... | | 1702| hot and dry | .... | | 1703| .... | .... | | 1704| dry Europe | .... | | 1705| .... | .... | | 1706| hot, dry Europe | .... | | 1707| very hot | .... | | 1708| .... | very severe | | 1709| .... | .... | | 1710| .... | .... | | 1711| .... | cold Europe | | 1712| wet England | .... | | 1713| wet England | mild | | 1714| dry and hot | .... | | 1715| dry | .... | | 1716| very dry | severe | | 1717| .... | severe | | 1718| hot and wet | .... | | 1719| .... | cold America | | 1720| dry Europe | .... | | 1721| .... | .... | | 1722| cold, wet | .... | | 1723| .... | cold | | 1724| wet England | .... | | 1725| wet England | .... | | 1726| .... | .... | | 1727| dry, hot Amer. | .... | | 1728| hot Amer. | severe Europe | | 1729| .... | .... | | 1730| .... | very cold Eng. | | 1731| .... | .... | | 1732| .... | severe Amer. | | 1733| dry Eng. | .... | | 1734| .... | .... | | 1735| wet | .... | | 1736| wet | .... | | 1737| .... | very severe Am. | | 1738| .... | .... | | 1739| wet England | very severe Eng. | | 1740| .... | very severe Am. | | 1741| .... | .... | | 1742| .... | severe Syria | | 1743| hot | .... | | 1744| .... | .... | | 1745| .... | .... | | 1746| .... | .... | | 1747| hot and dry | severe | | 1748| dry | .... | | 1749| very dry | .... | | 1750| very hot | very severe | | 1751| wet England | severe Amer. | | 1752| very hot Amer. | .... | | 1753| .... | severe | | 1754| .... | mild Amer. | | 1755| .... | severe Europe | | 1756| .... | severe Syria | | 1757| .... | .... | | 1758| hot | .... | | 1759| .... | severe | | 1760| .... | .... | | 1761| very dry Amer. | .... | | 1762| very dry Amer. | severe | | 1763| .... | .... | | 1764| hot Europe | .... | | 1765| hot Europe | severe Europe | | 1766| hot and dry Eur. | very severe | | 1767| .... | cold | | 1768| hot | .... | | 1769| hot | .... | | 1770| wet England | .... | | 1771| wet Am. & Eng. | cold Europe | | 1772| hot America | Am., great snow | | 1773| .... | .... | | 1774| .... | severe Europe | | 1775| .... | .... | | 1776| hot | severe Europe | | 1777| .... | .... | | 1778| hot | mild | | 1779| hot Eng. | very severe | | 1780| .... | .... | | 1781| .... | .... | | 1782| dry Amer. | .... | | 1783| hot | very severe | | 1784| hot | .... | | 1785| dry Europe | cold | | 1786| cool | cold | | 1787| cool | .... | | 1788| rainy Amer. | cold | | 1789| cool spring, hot summer | severe Eur., mild Amer. | | 1790| .... | .... | | 1791| very hot Am. | cold | | 1792| .... | .... | | 1793| hot, dry Am. | mild Amer. | | 1794| .... | severe Europe | | 1795| Amer., hot, rainy | .... | | 1796| Autumn very Dry Am. | cold Amer. | | 1797| cool Am. | severe Amer. | | 1798| very hot } | { long & severe | | 1799| very dry Am. } | { Amer. & Eur. | +---------------------------------------------------------+

Still more definite evidence is found in the meteorological tables of Dr. Holyoke and Dr. Hildreth, and an account, by Dr. Hildreth, of the seasons when the Ohio River was closed or obstructed by ice, found in Silliman's Journal, new series, vol. xiii. p. 238.

Thus, we have, from the tables of Dr. Holyoke, the following annual means, from 1786 to 1825, inclusive. I have arranged them in periods of five years. It will be seen that there are three peculiarities observable. First, a marked difference between the first and second periods of the decade, corresponding, generally, with the presence or absence of the spots. Second, a difference in the mean of the decades which may well be supposed to correspond with the difference in the number or size of the spots since a like difference is observable in number and size, and the time when they reached their maxima and minima, in the table of Schwabe. And, third, there are occasional single cold years during the warm period, and these correspond with what the tables of Dr. Webster show for both the sixteenth and seventeenth centuries. In relation to this, it should be remembered that volcanic action is a frequent and powerful disturber of the regular action of terrestrial magnetism, and that the extremes, for that reason, are frequently meridional or local and alternating; and to that cause very great extremes, and marked exceptions, may be due, notwithstanding the spots upon the sun may exert an influence in producing hot summers and cold winters toward the close of each decade. Thus, to select an instance to illustrate this and explain an anomaly: The coldest season during the whole period, embraced in the following tables, is that of 1812. This occurs during the decrease of spots, and the warm half of the decade. Turning to the table of volcanic action, and of earthquakes, found in the Report of the British Association for 1854, we find that year was remarkable for earthquakes in the United States and South America. In December, 1811, earthquakes commenced in the valley of the Mississippi, Ohio, and Arkansas, felt also at places in Tennessee, Kentucky, Missouri, Indiana, Virginia, North and South Carolina, Georgia, and Florida, though not so severely east of the Alleghanies, which continued until 1813. About the same time they commenced in Caraccas, and, in March, 1812, became severe over the greater portion of the northern section of South America, and in the Atlantic. No such general and continued succession of earthquakes occurred during the other periods embraced in the tables, and the mean of the following five years was very low, embracing the memorable cold summer of 1816.

+---------------------------------------------------------------+ | Cold Period. | Warm Period. | Cold Period. | Warm Period. | |---------------|---------------|---------------|---------------| |1786 48 deg..53 |1791 48 deg..963|1796 48 deg..678|1801 50 deg..432| |1787 47 deg..88 |1792 48 deg..44 |1797 48 deg..135|1802 50 deg..794| |1788 47 deg..676|1793 50 deg..96 |1798 49 deg..471|1803 50 deg..24 | |1789 47 deg..68 |1794 50 deg..768|1799 48 deg..291|1804 48 deg..328| |1790 46 deg..53 |1795 50 deg..173|1800 49 deg..989|1805 50 deg..792| |---------------|---------------|---------------|---------------| |Mean of | | | | |period 47 deg..659|Mean 49 deg..901|Mean 48 deg..910|Mean 50 deg..117| |---------------|---------------|---------------|---------------| |---------------|---------------|---------------|---------------| |1806 47 deg..982|1811 50 deg..76 |1816 47 deg..113|1821 48 deg..15 | |1807 48 deg..132|1812 45 deg..28 |1817 46 deg..277|1822 49 deg..81 | |1808 49 deg..485|1813 47 deg..702|1818 48 deg..009|1823 47 deg..58 | |1809 47 deg..92 |1814 48 deg..279|1819 50 deg..75 |1824 49 deg..25 | |1810 49 deg..001|1815 47 deg..607|1820 48 deg..70 |1825 50 deg..99 | |---------------|---------------|---------------|---------------| |Mean 48 deg..505|Mean 47 deg..925|Mean 48 deg..169|Mean 49 deg..15 | +---------------------------------------------------------------+

The tables of Dr. Hildreth, from 1826 to 1854, inclusive, furnish, generally, evidence of a like character. There are, however, an anomaly or two which will be observed. From 1826 to 1830, the mean is high during the period when spots were at a maximum. But that maximum embraced a much less number of spots than the two succeeding ones. A contrast appears in the tables of Dr. Hildreth, during the early period, for Dr. Holyoke's register, for 1827, puts it below the mean, but Dr. Hildreth's one of the highest of the half century. In 1835 commenced a period when the spots were much more numerous, and from 1835 to 1838, inclusive, the seasons were correspondingly below the mean. From that period to 1844 a gradual and slightly irregular rise took place, excepting the year 1843, when another cold year intervened. The table of earthquakes, published by the British Association, closes with 1842, and I have not access to any others. The occurrence of such cold years, in the warm period, at intervals during the two centuries previous, and in 1812, and onward, and evidently owing to increased volcanic action beneath the western portion of the northern hemisphere, justifies the belief that the low temperature of 1843 was owing to the same cause. The following are the means from the tables of Dr. Hildreth:

+----------------------------------------------------------------+ |1826 54 deg..00|1831 50 deg..87|1836 50 deg..03|1841 52 deg..18|1846 53 deg..64| |1827 54 deg..92|1832 52 deg..42|1837 51 deg..57|1842 52 deg..83|1847 52 deg..00| |1828 55 deg..22|1833 54 deg..56|1838 50 deg..62|1843 50 deg..77|1848 52 deg..50| |1829 52 deg..38|1834 52 deg..40|1839 52 deg..54|1844 53 deg..25|1849 52 deg..09| |1830 54 deg..93|1835 50 deg..65|1840 52 deg..35|1845 52 deg..73|1850 51 deg..48| |------------|------------|------------|------------|------------| |Mean 54 deg..29|Mean 52 deg..18|Mean 51 deg..52|Mean 52 deg..35|Mean 52 deg..32| +----------------------------------------------------------------+

The observations of Dr. Holyoke were made at Salem, Massachusetts; those of Dr. Hildreth at Marietta, Ohio.

The following, in relation to the freezing of the Ohio River, is evidence of a different kind, but shows the same general correspondence, and particularly the mildness of the winters when there were few spots, and their severity from 1836 to 1838, inclusive, when the spots were most numerous:

1829.--River open all winter--some floating ice. 1830.--River closed 27th January. 1831.--Floating ice--closed 23d January--opened 20th February. 1832.--Closed in December, which was a very cold month--opened January 8, and remained open all winter. 1833.--Open all winter. 1834.--Open all winter. 1835.--Closed January 6--opened the last of the month--cold. 1836.--Closed 28th January--opened 25th February. 1837.--Closed from 8th December to 8th February. Cold year. 1838.--Closed from 13th January to 13th March. Cold year. 1839.--Closed from 6th December to 13th January. 1840.--Closed 29th December--opened 15th January. 1841.--Closed 3d January--opened 8th do. 1842.--Open all winter. 1843.--Closed 28th November--opened 5th December--open all the rest of the winter. 1844.--Open all winter. 1845.--Open all winter. 1846.--Closed 5th December--opened again a few days--closed again on the 26th. It is not stated how long it remained closed. 1847.--Open all winter. 1848.--Much floating ice, but not closed--heavy rains and floods. 1849.--Floating ice in January, but not closed. 1850.--Floating ice, but not closed. 1851.--Open all winter--a little ice.

(December in the above table, means December previous).

This is more reliable as to the winter season than the tables of annual means--although the evidence they afford, making due allowance for the exceptions, is very striking.

I shall return to this part of the subject again.

But there is other evidence of the influence of these spots. Their connection with the irregular magnetic disturbance of the earth has been distinctly traced. Colonel Sabine, President of the British Association, in his opening address, September, 1852, after reviewing the recent discoveries in magnetism, says:--

"It is not a little remarkable that this periodical magnetic variation is found to be identical in period, and in epochs of maxima and minima, with the periodical variation in the frequency and magnitude of the solar spots, which M. Schwabe has established by twenty-six years of unremitting labor. From a cosmical connection of this nature, supposing it to be finally established, it would follow that the decennial period, which we measure by our magnetic instrument, is, in fact, a solar period, manifested to us, also, by the alternately increasing and decreasing frequency and magnitude of observations on the surface of the solar disc. May we not have in these phenomena the indication of a cycle, or period of secular change in the magnetism of the sun, affecting visibly his gaseous atmosphere or photosphere, and sensibly modifying the magnetic influence which he exercises on the surface of our earth?"--American Journal of Science, new series, vol. xiv. p. 438.

I think it may fairly be inferred, that although these spots do not occasion the "cold spells" and "hot spells," and other transient peculiarities, they do materially affect the mean temperature of the year, and exert an obvious influence when at their maxima; and there is a tendency to an increase of the heat and dryness of summer, and the severity of winter, at the periods named, in our excessive climate, and a well-established connection between the spots and magnetic disturbances and variations.

Popular opinion has ever attributed to the moon a controlling effect upon the changes of the weather. If it be dry, a storm is expected when the moon changes; or if it be wet, dry weather. Such popular opinions are usually entitled to respect, and founded in truth. But every attempt to verify this opinion, by careful observation and registration, has failed. Weather-tables and lunar phases, compared for nearly one hundred years, show four hundred and ninety-one new or full moons attended by a change of the weather, and five hundred and nine without. The celebrated Olbers, after fifty years of careful observation and comparison, decided against it. So did the more celebrated Arago, at a more recent date--summing up the result of his observations by saying--"Whatever the progress of the sciences, never will observers, who are trustworthy and careful of their reputation, venture to foretell the state of the weather." Still, the moon may influence the weather, though she may not effect changes at her syzygies or quadratures, and this subject should not be too summarily dismissed. That the moon can not effect changes at the periods named seems philosophically obvious. She changes, for the whole earth, within the period of twenty-four hours; yet, how varied the state of things on different portions of its surface. The equatorial belts of trades, and drought, and rains, cover from fifty to sixty degrees of its surface, and know nothing of lunar disturbance. The extra-tropical belt of rains and variable weather moves up in its season, uncovering 10 deg., or more, of latitude, and admitting the trades and a six months' drought over it, as in California, regardless of the moon. Under the zone of extra-tropical rains, even upon the eastern part of the continent of North America, "dry spells" and "wet spells" exist side by side; the focus of precipitation is now in one parallel, and now in another--storms exist here and fair weather there, on the same continent at the same time; and as the moon's rays in her northing pass round the northern hemisphere during the twenty-four hours, they, doubtless, pass from ten to thirty or more storms, of all characters and intensities, moving in opposition to her orbit--and as many larger intervening areas of fair weather, not one of which are indebted to her for their existence, or "take thought of her coming."

The storm, which originates in the tropics, pursues its curving way now N. W., then N. E., and again north, to the Arctic circle, and, perhaps, around the magnetic pole, over gulf, and continent, and ocean, occupying one third the time of a lunation, and two changes, perhaps, in its progress, without any perceptible or conceivable influence from her. Yet every inhabitant of mother-earth, influenced by coincidences remembered, and uninfluenced by exceptions forgotten, looks up within his limited horizon, and devoutly expects from the agency of some phase of the moon, a change for the special benefit of his dot upon the earth's surface. Upon how many of these countless dots is the moon at a particular phase, or relative distance from the sun, to change fair weather to foul, or foul to fair? Upon none. The storms keep on their way;--the wet spells, and the dry spells, the cold and the hot spells alternate in their time, and though the moon turns toward them in passing, her dark face, her half face, or her full orb (the gifts of the sun, which confer no power), they do not heed her. They are originated, and are continued, by a more potent agent. They are the work of an atmospheric mechanism, as ceaseless in its operation as time, as regular as the seasons, as extensive as the globe.

Indeed, it seems as if it was expressly designed by the Creator that the moon should not interfere materially with this atmospheric machinery. She is the nearest orb; her influence would be controlling and continuous; would follow her monthly path from south to north, and with changes too violent, and intervals too long; and would interfere with the regular fundamental operation in the trade-wind region, where she is vertical. Aside from the attraction of gravitation, therefore, she seems to have been so created as to be incapable of exerting any influence. She is without an atmosphere; the rays which she reflects are polarized, and without chemical or magnetic power; and, if it be true that Melloni has recently detected heat in them, by the use of a lens three feet in diameter, which could not previously be effected, its quantity is exceedingly small, and incapable of influence. Doubtless, the attraction of her mass is felt upon the earth, as the tides attest; and upon the atmosphere as well as the ocean. But the atmosphere is comparatively attenuated, and exceedingly so at its upper surface. Her attraction, therefore, although felt, is not influential. She seemed, to Dr. Howard, to produce in her northing and southing, a lateral tide which the barometer disclosed, but owing to the attenuated character of the atmosphere, neither the sun nor moon create an easterly and westerly tide, that is observable, except with the most delicate instruments. Sabine is believed to have detected such a tide by the barometer, at St. Helena, of one four thousandth of an inch. But even this infinitesimal influence may prove an error upon further investigation. There is a diurnal variation of the barometer, but it is not the result of her attraction, for it is not later each day as are the tides, exists in the deepest mines as well as upon the surface, and is demonstrably connected with the group of diurnal changes produced by the action of the sun-light and heat upon the earth's magnetism.

Can the lateral tide, if there be one, affect the weather? for in the present state of science it seems entirely certain that the moon can exert an influence in no other way.

If the received idea of many, perhaps most, meteorologists, on which all wheel barometers are constructed, that a high barometer necessarily produces fair weather, and a low one foul, were true, she certainly might do so. But that idea can not be sustained, and there is no known certain influence exerted by the moon upon the weather, in relation to which we have any reliable practical data.

Humboldt appears to have adopted the impression of Sir W. Herschell, that the moon aids in the dispersion of the clouds. (Cosmos, vol. iv. p. 502.) But the tendency to such dispersion is always rapid during the latter part of the day and evening, when there is no storm approaching, and the full moon renders their dissolution visible, and attracts attention to them. The Greenwich observations, also, carefully examined by Professor Loomis, fail to confirm the impression of Herschell and Humboldt, and those eminent philosophers are doubtless in this mistaken.

From this general and somewhat desultory view of the general facts, which bear analogically upon the question, no decisive inference can be drawn in relation to the seat of the primary influence which produces the atmospheric changes. The preponderance is in favor of the magnetic, or magneto-electric, action of the earth. We must come back to our own country and grapple with the question at home.