David Rittenhouse.[[119]]
To Rev. Dr. Smith.”
The result of the Norriton Observations of the Transit of Venus—as well as those also made under the auspices of the American Philosophical Society, at Philadelphia and Cape Henlopen—will be found, in detail, in the first volume of the Transactions of that Society.[[120]] And “the Work itself,” to which Dr. Smith refers, in his Report of the Proceedings of the Norriton Committee, bears ample testimony to the transcendent Astronomical Abilities of Mr. Rittenhouse.—Four days after the Transit, Dr. Smith transmitted to the Hon. Mr. Penn, in London, a short account of the Norriton Observations, more particularly mentioning the times of the Contacts, and a few other circumstances attending them. This was speedily communicated by Mr. Penn to the Rev. Mr. Maskelyne,[[121]] the Astronomer Royal; who, acknowledging the receipt of the communication, by a note, dated at Greenwich the 2d of August, 1769, says—“I thank you for the account of the Pennsylvania Observations (of the Transit,) which seem excellent and complete,[[122]] and do honour to the gentlemen who made them[[123]], and those who promoted the undertaking;— among whom, I reckon yourself[[124]] in the first place.”[[125]]
Here the observation will emphatically apply;—Laus est, â viro laudato laudari.
Before this interesting occurrence in the life of Mr. Rittenhouse is finally passed over, the reader’s attention is solicited to the beautiful and animated description given by Dr. Rush, in his Eulogium, of the sensations which must have been more particularly experienced by that extraordinary man, on the near approach of the long-expected Phænomenon.—“We are naturally led here,” says the learned Professor, “to take a view of our Philosopher, with his associates, in their preparations to observe a phænomenon which had never been seen but twice[[126]] before, by any inhabitant of our earth, which would never be seen again by any person then living, and on which depended very important astronomical consequences. The night before the long-expected day, was probably passed in a degree of solicitude which precluded sleep. How great must have been their joy, when they beheld the morning sun!—‘and the whole horizon without a cloud;’ for such is the description of the day, given by Mr. Rittenhouse, in the report referred to by Dr. Smith. In pensive silence and trembling anxiety, they waited for the predicted moment of observation: it came,—and brought with it all that had been wished for, and expected, by those who saw it.—In our Philosopher, it excited—in the instant of one of the contacts of the planet with the sun, an emotion of delight so exquisite and powerful, as to induce fainting. This,” then remarks Dr. Rush, “will readily be believed by those who have known the extent of that pleasure which attends the discovery, or first perception of Truth.”
On the 9th of November, following, there was a Transit of Mercury over the Sun. An account of this phænomenon,—as observed at Norriton by William Smith[Smith], d. d. John Lukens, Esq. and Messrs. David Rittenhouse and Owen Biddle, the Committee appointed for that Observation by the American Philosophical Society,—was drawn up and communicated to the Society, by direction and in behalf of the Committee, by Dr. Smith: this will be found in the first volume of the Society’s Transactions. In this report it is remarked, that—“the first time that ever Mercury was observed on the Sun’s disk, was by Gassendus at Paris, October 28th 1631, O. S. and that the Transit of Nov. 9th was the fourth in that class; the two intermediate ones, each at forty-six years distance, having been observed by Dr. Halley, in 1677 and 1723.”
Mr. Maskelyne, the celebrated English Astronomer before mentioned,[[127]]—in a letter to Dr. Smith, of the 26th of December, 1769—expressed a wish “that the difference of Meridians of Norriton and Philadelphia, could be determined by some measures and bearings, within one-fiftieth or one-hundredth part of[of] the whole; in order to connect,” continues Mr. Maskelyne, “your observations of the Longitude of Norriton with those made by Messrs. Mason and Dixon, in the course of measuring the degree of Latitude.”—This request of the Astronomer Royal was communicated to the Philosophical Society of Philadelphia; in consequence of which, Dr. Smith, Mr. Lukens and Mr. Rittenhouse, were appointed to make the terrestrial measurement required. These gentlemen, having taken to their assistance Mr. Archibald M’Clean and Mr. Jesse Lukens, two able and experienced Surveyors, commenced their operations at Norriton, early on the 2d day of July following, and completed their survey on the 4th day of that month. The Report of the able Committee, to which this business was assigned by the American Philosophical Society, is also contained in the first volume of the Transactions of that learned Body. After giving various calculations, resulting from the operations of that committee, the Reporter says—“Hence, by the above measurement and work, we get Norriton Observatory 52″ of time West of the Observatory in the State-house Square; which is exactly what we got by that excellent element, the external contact of Mercury with the Sun, Nov. 9th 1769.”—“The external contact,” continues the Reporter, “gave it something more; owing, no doubt, to the difference that will arise among Observers, in determining the exact moment when the thread of light is compleated: and the mean of all our Observations gives the difference of Meridians, between Norriton and Philadelphia, only 4″ of time more than the terrestrial measurement, and the external contact of Mercury, gave it,—which may be taken as a very great degree of exactness; if we consider that the difference of Meridians, between the long-established Observatories of Greenwich and Paris, (as Mr. De la Lande writes, Nov. 18th 1762,) was not then determined within 20″ of time—For, he says, ‘some called it 9′ 15″; others, 9′ 40″;’ but that he himself commonly used 9′ 20″, though he could not tell from what Observations it was deduced.[[128]]—Finally, the Report fixes Philadelphia to be 5h 0′ 37″, and Norriton, 5h 1′ 29″ West from Greenwich.[[129]] The Latitude of Norriton, as deduced from the actual mensuration just mentioned, connected with Observations previously made by Mr. Rittenhouse—predicated also, in part, on antecedent Calculations of Messrs. Mason and Dixon, who, (having been furnished with a complete Astronomical Sector,) had ascertained the southernmost point of the City of Philadelphia to be in Latitude 39° 56′ 29″,4. N.—is stated, in the same Report, as being 40° 9′ 31″. It came out, by the measurement, 25″.09 less North, with respect to the southernmost point of Philadelphia, than Mr. Rittenhouse’s Observations had given it; and, in making these, he had no better Instrument than Sisson’s two-and-an half feet Quadrant. Nevertheless, the framer of the Report remarks, “as both were fixed by celestial observations and experienced Men, the small difference ought perhaps to be divided; and if a mean be taken, to reconcile it with the terrestrial measure, the Lat. of the south point of Philadelphia would be 39° 56′ 42″; and that of Norriton, 40° 9′ 43″.[[130]]
The same Volume of the American Philosophical Transactions that comprehends the communications of these Proceedings—as well as various Observations, made at different places, on the then recent Transit of Venus—contains also a Memoir, by Dr. Smith, deducing the Sun’s Parallax from a comparison of the Norriton and some other American Observations of the Transit of Venus, in 1769, with the Greenwich and some other European Observations of the same: And with this paper, its learned writer has incorporated a communication, on the same subject, made to him by Mr. Rittenhouse.
Until about the period at which the latest of these favourite transactions of Mr. Rittenhouse took place—namely, his geometrical employment in ascertaining the Latitude and Longitude of Norriton and Philadelphia, respectively,—he continued to reside on his farm at Norriton. And here he still carried on, with the aid of some apprentices and journey-men, his self-acquired occupation of a Clock and Mathematical Instrument-maker: combining, at intervals, with these mechanical pursuits, an unceasing attention to his philosophical studies and researches; and occasionally employing himself, principally with a view to his health, in some of the occupations of Husbandry. Ever an economist of Time, of which he well knew the inestimable value, none of his hours which could be spared from necessary sleep were suffered to be unemployed. In this rural abode, he enjoyed the comforts of domestic life amidst his little family, consisting only of an amiable wife and two young children. In short, no part of his time was unengaged, or uselessly passed; although he, not unfrequently, felt the solace of friendly calls, and was gratified by visits from persons of science, worth, and distinction.
The writer of these memoirs designed to narrate those circumstances most worthy of notice, in the Life and character of Mr. Rittenhouse, in their chronological order; and this plan will be generally adhered to. Having followed our philosopher in his astronomical and mechanical pursuits, up to the year 1770, it therefore becomes proper to recur to a period of his life some few years earlier, in order to introduce the history of his Orrery,[[131]] before mentioned; a piece of mechanism which is admitted, by all competent judges of its merit, to be one of the greatest of his works.