[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.
[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:[[97a]] 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.”
[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.
[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 5h 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.[[98a]]
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.