In the year 1782, Mr. Rittenhouse was elected a Fellow of the Academy of Arts and Sciences, of Boston: his certificate bears date the 30th of January, in that year. This academy, which Dr. Morse ranks among the first literary institutions in the state of Massachusetts, holds a very respectable station in relation to science: yet it was not established till so lately as May 4, 1780. The end and design of the institution are stated to be—“to promote and encourage the knowledge of the antiquities of America, and of the natural history of the country, and to determine the uses to which its various natural productions may be applied: also, to promote and encourage medical discoveries, mathematical disquisitions, philosophical enquiries and experiments; astronomical, meteorological and geographical observations, improvements in agriculture, arts, manufactures, commerce, and the cultivation of every science that may tend to advance a free, independent and virtuous people.”[[211]]
It is supposed to have been somewhat about this time, that Mr. Rittenhouse exercised his ingenuity upon an object, which, though not of great importance, is nevertheless a matter of considerable utility and some curiosity; the invention of an Hygrometer, made wholly of wood. The simplicity of the construction of this instrument, renders it easily attainable by almost every one; and as it is found to answer, very well, the end for which more expensive instruments are often employed, it may be considered as being more generally useful. Descriptions of the construction, and principle of operation, of this Hygrometer, having been furnished to the writer through the obligingness of two of his friends,[[212]] a very concise account of it, drawn up from those descriptions, is given in the Appendix.
A circumstance shall be noticed in this place, which, although trivial in itself, will serve to shew the grateful sense entertained by our Philosopher of the merits of General Washington. It appears, that just about the time when the provisional articles of peace, concluded on between the United States and Great-Britain, were made known in America, Mr. Rittenhouse had forwarded to the General, at the head-quarters of the army, a pair of spectacles, and reading glasses,—as a small testimonial of his respect for the character and services of that great man. The terms of the letter that accompanied this little present, are not known to the writer of these memoirs; but, of what complexion they were, may be inferred from the General’s answer, which is in these words:
“Newburgh, 16th Feb. 1783.
“Sir,
“I have been honoured with your letter of the 7th, and beg you to accept my sincere thanks, for the favor conferred on me, in the Glasses—which are very fine; but more particularly, for the flattering expressions which accompanied the present.
“The Spectacles suit my eyes extremely well—as I am persuaded the Reading-Glasses also will, when I get more accustomed to the use of them. At present, I find some difficulty in coming at the proper focus; but when I do obtain it, they magnify perfectly, and shew those letters very distinctly, which at first appear like a mist—blended together and confused. With great esteem and respect, I am, Sir, your most obedient and humble servant,
“Go. Washington.
“David Rittenhouse, Esq.”
The grinding and polishing of the glasses were of Mr. Rittenhouse’s own workmanship; and they were made for the purpose. This circumstance, added to the manner and occasion of their being presented, could not fail of being highly acceptable to the General.