“If it shall be thought proper, the whole is to be adapted to, and kept in motion by, a strong pendulum-clock; nevertheless, at liberty to be turned by the winch, and adjusted to any time, past or future.”
“N. B. The diurnal motions of such planets as have been discovered to revolve on their own axes, are likewise to be properly represented; both with regard to the Times, and the situation of their Poles.”
The foregoing is a literal copy of the original manuscript; and such readers of this article as may think proper to compare it with the printed description of Mr. Rittenhouse’s Orrery, communicated to the American Philosophical Society by Dr. Smith, on the 21st of March 1768, and contained in the first volume of that Society’s Transactions, will find some (though, on the whole, not very essential) differences, in the two descriptions. The concluding paragraph, indeed,—designated, in each, by a N. B.—is materially variant in the two: and it appears, by its having been announced in the published (and later) account of this machine, that, “the clock part of it may be contrived to play a great variety of Music,” (a suggestion wholly omitted in Mr. Rittenhouse’s original communication, made to the Rev. Mr. Barton,) that the philosophic Artist had been afterwards induced, in one particular at least, “to comply with the prevailing taste.”[[140]] But this may be readily accounted for: our artist had previously made some extremely curious and beautiful Time-pieces, to each of which was attached the mechanism of a Musical Clock, in addition to a limited Planetarium, in miniature. These were in the hands of gentlemen of respectability and taste:[[141]] and they were much and generally admired, as well for the great ingenuity displayed by the constructor, in these combined and pleasing operations of his machinery, as for the superior accuracy and beauty of the workmanship; qualities eminently conspicuous in all his mechanical productions.
It appears, that when Mr. Rittenhouse sent the foregoing description of his projected Orrery to Mr. Barton—that is to say, on the 27th of March, 1767[[142]]—the “foundation” of it was “laid.” But, notwithstanding his earnest wishes prompted him to the utmost diligence, in his exertions to finish it, many circumstances concurred to retard its completion. The magnitude of the undertaking—the multiplicity of the work—and, perhaps, the difficulty of sometimes readily procuring, even from Philadelphia, the necessary materials,—all conspired, to prevent as early a completion of the machinery as he had anticipated: and, added to these causes of unavoidable delay, was the yet unabandoned pursuit of his professional business.
The Orrery was, nevertheless, then his favourite object. On the 18th of June, 1767, he wrote to Mr. Barton, thus—“I hope you will persuade your Pequea friends to stay for the clocks, till harvest is over; and then, I think, I may venture to promise them, for ready money: but, at this time, one part of the Orrery is in such forwardness, that I am not willing to lay it by till it is done. I hope it will far exceed the description I gave you of it. To-morrow morning I am to set off for Reading, at the request of the Commissioners of Berks county, who wrote to me about their town-clock. They had employed a ... to make it, who, it seems, is not able to go through with it: if I should undertake to finish it, this will likewise retard the great work.”
Amidst the more important philosophical pursuits which engaged Mr. Rittenhouse’s attention before his removal to Philadelphia, as well as after he fixed his residence in that city, he now and then relaxed the energy of his mind from its employment in laborious investigations, by bestowing a portion of his time on minor objects in physical science; and indeed, sometimes, even on little matters of ingenuity, curiosity and amusement. As instances of this, he addressed to the Rev. Mr. Barton the letter under the date of the 20th of July, 1768, which will be found in the Appendix; and also another, dated the 4th of February, 1770, to which there is the following postscript:
“I have,” says he, “seen a little curiosity, with which you would be pleased; I mean the glass described by Dr. Franklin, wherein water may be kept in a boiling state, by the heat of the hand alone, and that for hours together. The first time I shall be in Lancaster, where I hope to be next June, I expect to prevail on you to accompany me to the Glass-house,[[143]] where we may have some of them made, as well as some other things I want.”—A description of this instrument, then usually called Dr. Franklin’s Pulse-Glass,[[144]] by means of which water may be made to boil, in vacuo, by the heat of the human hand, was communicated by Mr. Rittenhouse to Mr. Barton in a subsequent letter.