Part 25

Within our own day and a short period of time preceding it, great improvements have been made in the construction of the pendulum-clock, as well as in other descriptions of Chronometers. Mr. Rittenhouse’s early zeal in his practical researches into astronomy, prompted him to desire the greatest possible accuracy in the construction of time-pieces adapted to astronomical purposes; and uniting, as he did, operative skill with a thorough knowledge of the principles upon which their construction depends, he was enabled—impelled by so powerful a motive—to display to the world, by his own manual ingenuity, the near approach to perfection to which the pendulum-chronometer may be brought. Besides his astronomical pursuits, his early employment in ascertaining the limits and fixing the territorial boundaries of Pennsylvania, and of some of the neighbouring states, obliged him to supply himself with chronometers of the greatest possible accuracy: and these were either made by his own hands, or under his immediate inspection by his brother, who, with the aid of his instruction, became an excellent mechanician. One of these fine instruments, bearing on its face the name of Benjamin Rittenhouse as the maker, and the date of the year 1786, is now in the possession of Mr. Norton Prior, of Philadelphia: but that admirable one, the workmanship of which was executed by our Philosopher himself, and which was part of the apparatus of his Philadelphia Observatory, is now placed in the hall of the American Philosophical Society. This is constructed on a greatly improved plan of his own, which improvement was afterwards applied to that now belonging to Mr. Prior; and the latter is the same chronometer, it is believed, that was used by Mr. D. Rittenhouse, in fixing the northern line which divides Pennsylvania from New York, and in establishing the boundary line between the last mentioned state, and Pennsylvania and Massachusetts, respectively, in the years 1786 and 1787.—A description of the principles of his observatory-chronometer here mentioned, together with some account of its mechanism, will be found in the Appendix: the former having been communicated to the writer of these memoirs by the ingenious Robert Patterson, Esq. director of the Mint; and the latter by that able mechanician, Mr. Henry Voight, chief coiner in that institution,—a person who, by reason of his well-known skill as a clock and watch-maker, was employed by Mr. Rittenhouse more than forty years since, in the fabrication of some of his philosophical instruments.

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Footnote 96:

The first pendulum-clock made in England, was in the year 1662, by Mr. Fromanteel, a Dutchman.

In the library-hall of the Philadelphia Library-Company, is one of the clocks made by that artist, having this inscription engraven on its face, “Johannes Fromanteel, Londini, fecit;” but without any date. This clock was a donation to the library-company, in the year 1804, by Mr. Samuel Hudson, of Philadelphia, whose ancestor purchased it at an auction in London, after the restoration of king Charles II. The traditional account of it is, that it belonged, originally, to the Cromwell family; and, when presented, was said to be one hundred and forty years old: but it could not have been the property of the protector, Cromwell, the time of whose death was between three and four years anterior to Fromanteel’s construction of a pendulum-clock.

Footnote 97:

Besides the testimony of so distinguished an astronomer as Mr. de Zach, already given, respecting the very great accuracy to which time-keepers have been brought, the following translation, taken from what the celebrated Lalande has said in his treatise Des Horloges Astronomiques, (in the second volume of his Astronomie,) furnishes some curious and interesting facts on that subject.

“Short (the mathematical instrument maker,) upon the occasion of the transit of mercury over the sun observed in 1753, assures us that he had found by many observations, that his clock had not varied more than one second, from the 22d of February to the 6th of May (Philos. Trans. 1753, p. 200;) so that, with a like pendulum, it is possible to obtain an exactness which, till this time, was thought incredible. There are English astronomers who have assured me,” continues Lalande, “that pendulum-clocks have been made which did not vary more than five″ in a year: but that does not appear to me to be yet established as a fact; the oils that one is obliged to use in them are sufficient, by the change of consistency they undergo, to prevent such preciseness. The count de Bruhl, a great amateur and a perfect connoisseur also, on the subject of time-pieces, shewed me in London a diary of the going of two pendulums of Mudge, one of the most celebrated clock-makers in London: in one, there was a difference of half a second a day, between winter and summer; and in the other a second. Mr. Aubert has a pendulum made by Shelton, which varies also nearly a second in the day, in extreme seasons. Picard, in 1671, had a clock which did not lose a second in two months. But, whatever may have been, since that period, the skill of the clock-makers of Paris, we cannot obtain such exactness, but by mere accident and an equality of temperature in the atmosphere that is very rare: now, the correctness of our clocks is a necessary consequence of their principles; but these do not go so far. Mr. Emery has observed two clocks beat the same second, during three months; they were, however, very near to each other, and probably had some influence on one another by means of their foot-board or support.”

Footnote 97a:

Even watches have been already brought to an inconceivable degree of exactness. Mr. Arnold and Mr. Emery made some, in the year 1786, which did not vary one second in a voyage of an hundred leagues.

Footnote 98:

This gentleman’s name is connected with another circumstance in relation to Mr. D. Rittenhouse, which deserves to be noticed. He is in possession of a finely-graduated thermometer, made by our Philosopher; on the scale of which is engraved, by him, the record of a memorable fact concerning the climate of Pennsylvania, referring by a mark to 22° below 0, of Fahrenheit’s scale; viz.—“Jan. 2. 1762—Great Cold in Pennsylvania.” This fact was ascertained by Mr. Rittenhouse, from a reference to the accurate Messrs. Masons and Dixon’s Journal; in which, such was stated to have been the degree of cold in the forks of the Brandywine (about thirty miles westward, and very little to the southward, from Philadelphia,) on the day mentioned.

Mr. Rittenhouse had noticed, that, at his Norriton Observatory, (in lat. 40° 9′ 31″ N.) the mercury in Fahrenheit’s thermometer, not exposed to the sun-shine but open to the air, was at 94½°, on the 5th of July 1769; “which,” says he, “was the greatest height it had ever been observed to rise to, at that place.” But the writer is informed by a judicious and attentive observer, that at Lancaster, Pennsylvania, which is in lat. 40° 2′ 39″ N. (the long. of this borough-town is 5^h 1′ 4″ W. from Greenw.) the mercury rose by Fahrenheit’s scale, on the 7th of July, 1811, to 97½°. Admitting this to be correct, if 1½° be then deducted, for the extra heat of so large a town as Lancaster in comparison with a country-situation, there is in this case the great range of 118° by Fahrenheit’s scale, for the extremes of heat and cold in Pennsylvania.

The writer brought with him, from England, a meteorological diary kept in London, during the severe frost there, from the 7th day of January, 1776, to the 28th of the same month, both days inclusive. The greatest cold, during that period, was 15° and it is thus noted, in respect to the state of the atmosphere at the time; “Clear sky—intense cold—wind west.” The mercury rose on one day, within that time, to 34°. The mean degree of cold, in the same period, was there 26¾°.

The greatest cold at Philadelphia, during the same days of January, 1776, was at 17°, but the mercury rose there, on one of those days, to 48°. The mean degree of cold at Philadelphia, in this corresponding period of time, was 29⅓°; being about 2½° warmer (or rather, less cold,) than the general temperature of the weather in London, at the same time, in what was there called a “severe frost.” Eighty-five degrees of Fahrenheit’s scale is considered as a very extraordinary heat, in London: consequently, a range of 68° may be presumed to reach the extremes of heat and cold in England, in the latitude of nearly 52° N.

Notwithstanding the extremes of heat and cold, which thus appear in the climate of Pennsylvania, Mr. Jefferson remarks (in his Notes on Virginia,) that these extremes are greater at Paris than at Williamsburg, the hottest part of Virginia. Yet Williamsburg, which is only about 2¾° to the southward of Philadelphia, is nearly 11¾° further south than Paris.

Footnote 98a:

Since writing the above, the author has ascertained, that in London, during the four last years of the last century, Six’s thermometer, out of doors, averaged 49.6; that on the hottest day within that period, the mercury rose to 86; and that it fell, on the coldest day, to 4.

Footnote 99:

See a description of this Chronometer, in the Appendix.

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The great accuracy and exquisite workmanship displayed in every thing belonging to the profession he pursued, that came through his hands, soon became pretty extensively known: and this knowledge of his mechanical abilities, assisted by the reputation he had already acquired as a mathematician and astronomer, in a short time procured him the friendship, respect and patronage, of some eminent scientific characters; while it promoted his interest, in the profession he had thus newly chosen. In this he was, nevertheless, self-taught; for he never received the least instruction from any person, in any mechanic art whatever: and, therefore, if he were to be considered as being merely an excellent artist, in an occupation intimately connected with the science of mathematics—untutored, as he was, in any art or science,—he would deservedly be deemed an extraordinary and eminent man. It will be perceived, however, that it was the union of the almost unbounded powers of his genius, and his prodigious acquirements in a sublime science, with his wonderful abilities as a philosophical mechanic—and these faculties and attainments, moreover, combined with an amiable and virtuous character,—which constituted that celebrity so justly attached to his name.

Our young philosopher lived a retired, though by no means an inactive life, in his father’s family, for several years after he arrived to (what is usually termed) lawful age. In this situation, which was a pleasant one in many respects, he long continued to enjoy the tranquil scenes of rural life, amidst the society of an amiable and very intelligent family-circle, and surrounded by many worthy and estimable neighbours, by whom he was both loved and respected. His chief occupation was the profession he had chosen; but in such occasional intervals of personal abstraction from the mechanical part of his business, as the assistance the workmen he employed enabled him to obtain, he devoted much of the time to philosophical pursuits and study. Frugal in his expenditures, his industry furnished him amply with the means of comfort; and in the plentiful and decent mansion of his father’s family he experienced, with contentment, almost every gratification that a reasonable mind could desire. Good health seemed alone to be wanting to complete his happiness, in his earlier years; a privation which he felt through the greater part of his life.

Such was the condition of Mr. Rittenhouse, while he remained under the same roof with his father and mother, and some of their unmarried children. It was a mode of life which his disposition was calculated to enjoy; for, strongly attached to his kindred and friends by the benevolence of his nature, he derived much of his happiness from the reciprocal affections of a domestic circle and the kind intercourses of friendly esteem.

There does not appear to have been, for a long time, any occurrence that could have much disturbed the placid composure of our philosopher’s mind,—until 1762; in which year his sister Anne died, in the twenty-sixth year of her age. She was the wife of Mr. George Shoemaker, a respectable citizen of Philadelphia, and a member of the religious society of Friends. A letter which Mr. Rittenhouse wrote to his brother-in-law Mr. Barton, in October 1762, announcing this event, indicates the keenness of his sensibility on the occasion. Mrs. Shoemaker was a woman of intrinsic worth; she died in the prime of life; and it is believed, she was the first of Mr. Rittenhouse’s affectionate little band of brothers and sisters who had attained to the age of maturity, that he had then lost. After giving a circumstantial account of his sister’s illness and death, he informs Mr. Barton, that Mr. Daniel Stanton, an eminent public speaker in the society of Friends, attended her in her last illness, at her particular request;—and, added Mr. Rittenhouse, “the same worthy gentleman who visited her in her sickness, delivered an excellent exhortation at the grave,—giving, in a few words, a very just character, I think, of our deceased sister.”

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Footnote 100:

Mr. Stanton died at Philadelphia, the 28th of June, 1770, aged sixty-two years. He was, for above forty years, a distinguished preacher among the people called Quakers; and is reputed to have been a man, “who, from his youth, had been a conspicuous example of Christian meekness, humility, and self-denial; a zealous promoter of the cause of religion, and the essential good of mankind.”