Part 2

Every now and then one comes forward with some skillfully carved jewel which he has wrought into shape to deck his shrine. Sometimes it is only a little piece merely good for inlaying the walls, yet it fits well in its place and strengthens the faith of other workers. Again it is the great keystone for some massive arch whose other stones were laid in bygone times. Yet again it is a mighty truth that will not fit in the great building at all until the wrong work be torn down, and then it forms the base for one of the steadfast and everlasting towers. So pure must be the faith of those who bow at the hallowed shrines of truth that they would tear down these shrines rather than let them stand upon, or even harbor error.

The writer gives in this little book a keystone which he knows will not fit in the present building unless some errors be torn out. Those whose faith is true will not waver nor come grudgingly to the work of rebuilding.

GEOLOGICAL AND SOLAR CLIMATES,

THEIR CAUSES AND VARIATIONS.

THE CAUSE OF THE ICE AGE.

“The most important problem in terrestrial physics * * and the one which will ultimately prove the most far reaching in its consequences, is: What are the physical causes which led to the Glacial Epoch and to all those great secular changes of climate which are known to have taken place during Geological Ages?” (Dr. Croll, Climate and Cosmology.)

“An attentive study of the physical Geography of the earth and its influences on Climate, together with a judicious application of the simplest physical theories, will enable us to gain by and by a better knowledge of Geological climates.” (Prof. A. Woeikof, Nature, March 2, 1882, p. 426.)

Since Agassiz announced the past existence of an age during which ice covered temperate and tropical land areas, the cause of this wonderful phenomenon has been a problem of profound interest. Upon the correct solution of it hinges also the cause of Geological climates.

So great has been the interest attaching to this subject, that more study has been devoted to it during the past fifty years than perhaps to any other in Geology; hardly a leading scientific magazine runs through a year’s numbers without one or more articles upon it; and no Geological Society is without zealous students of glacial phenomena. Some have become so absorbed in the subject that, led by the recurrence of certain slight astronomical influences, they recognize a glacial period for slight and widely scattered evidences of possible early local glaciation, forgetful of the fact that an era of frigid climate could not intervene between two eras of tropical climates without the intervention of eras of temperate climates.

The evidences establishing the reality of the Ice Age during the Quaternary period are now beyond dispute. It is difficult, however, to establish by geological evidence the synchronal glaciation of all the continental areas known to have been heavily glaciated. This difficulty arises from the fact that the identity of various strata has to be established by fossils of varying conditions and characters; it is also rare that the same geologist has visited and compared the evidence upon more than two continents, thus eliminating probable errors from unequal sub-aerial denudation and exposure in the different zones of present climates and upon different continents. Again, the proof of the contemporaneous existence of corresponding strata upon different continents in the same latitude is sometimes attempted by a comparison of land fauna and flora, with marine fauna and flora, or even by more complex comparisons. Fossil plant life is by far more reliable than animal life for comparative purposes.

Another misleading factor is found in the interpretation of the great trans-continental lines of terminal moraines into the absolute limits of glaciation. Considering the great lapse of time since the removal of glacial conditions in temperate and tropical latitudes, it is more than probable that the existing unobliterated evidences by no means mark the extreme limits of a lighter and more extended glaciation whose traces have been destroyed, but which can justly be interpolated between the existing very marked traces of enormous glacial extension during Quaternary times. It is not impossible, nor entirely improbable, that early local glaciation did not occur during the early part of the Cenozoic Era, or even earlier, but the data upon which to establish the occurrence of such early local glaciation are both meagre and obscure. Should the evidences of such early local glaciation be developed beyond dispute, they will in no way interfere with the interpretation to be given, but they will strongly corroborate certain portions of this interpretation. So far as the author has been able to examine such evidence, it has been found to be between strata containing fossil life of a torrid character, with no evidences of a gradual merging into a temperate climate above and below it, as in Quaternary glaciation.

Before entering further into this discussion, it may not be out of place to briefly review the principal theories advanced to account for the Ice Age. It will be seen that physicists and astronomers have vied with geologists in the diligence of the search for the cause of this age, and their minds have been as fertile in the number of causes assigned as the true one. Not one of all the causes suggested has been sustained by argument without a flaw in the reasoning, and no demonstration has been made which has carried conviction to the scientific world.

It would not be instructive to attempt to review all of the theories which have been urged. The tendency to ascribe remote inadequate or obscure causes, rather than to interpret facts and phenomena in accordance with known laws, is apparent in many. Some writers have ascribed causes resting only upon hypotheses beyond the range of either analysis or investigation; such hypotheses can only stand in the absence or failure of all other assignable causes. Therefore the leading causes only will be briefly mentioned.

In a recent monograph on the subject, the following are given:

1. A decrease in the original heat of the globe.

2. Changes in the elevation of land, and consequent variations in the distribution of land and water.

3. Changes in the obliquity of the axis of the earth.

4. A period of greater moisture in the atmosphere.

5. Variations in the amount of heat radiated by the sun.

6. A variation in the heat absorbing power of the sun’s atmosphere.

7. Variations in the temperature of space.

8. A coincidence of an Aphelion winter with a period of maximum eccentricity of the earth’s orbit.

9. A combination of 8 and 2.

10. The views of Sir Robert Ball, LL. D., etc., as expressed in his recent work, The Cause of an Ice Age.

The first of these theories is universally admitted, and taught in even elementary works on Physical Geography, but it fails to account for all the phenomena accompanying the Ice Age, or to account for the disappearance of that age, and, so far as the author is aware, has not been presented in such form as to satisfactorily account for geological and present climates in rigid conformity with the facts and known laws. Nor has it been presented in such form as to account for that era of geological climates known as the Ice Age; moreover, it fails to account for the disappearance of that Age.

The second has been proved to be a local and correlated phenomenon, but cannot be accepted as a cause, since glaciation did not solely depend in the same latitudes upon elevation above sea level.

As to the third, whilst slight changes in obliquity have occurred, and must continue to occur, the results are too slight and the distribution of glacial phenomena is too general to warrant the acceptance of such change as a prime cause.

The fourth is a necessary consequence of the first, but, like the first, fails when the crucial test of accounting for the disappearance of the continental Ice Sheets is applied.