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. ----- Footnote 143: