TO DAVID RITTENHOUSE.
New York, June 30, 1790.
Dear Sir,—Your favor of the 25th came to hand last night, for which I give you many thanks. The conversion of 36.71428 pouces into 39.1923 inches, was an error in division, and consequently the mean taken between that and Graham's computation is wrong. It has rendered it necessary for me to suppress the note on that subject, and to put it into the form now enclosed. In this I state the reason for adopting 11-3 pouces as the equivalent of the English foot. It is so stated by D'Alembert in the Encyclopedie, and retained in the new Encyclopedie. To have changed it for 11-3.11 Mashelynci's measure, would have obliged me to have formed all my calculations anew, which would have exposed me to new errors of calculation; and added to the trouble and delay it would have occasioned, did not seem worth while for so small a fraction as 11-100 of a line, or the 1227th of a foot. I suppose, too, that the operation concerting between the French and English will soon furnish us with a new and more certain equation of their feet. I still like the rod rather than the pendulum, because I do not know a single objection to it which does not lie to the pendulum, because it is clear of some objections to which that is liable, but most of all, because 1-5 of the second rod is much nearer the present foot than 1-3 of the second pendulum. After all, should the French and English adopt the pendulum, we shall be free to do so also. I state on the enclosed paper a very loose answer to the 5th objection, which is the only one I can give. Can you suggest something more precise? As there is an idea that Congress will rise about the middle of July, I shall only await the answer you will be so good as to make to this, and then give in my report. This day, I fancy, will determine whether we are to be removed to Philadelphia or not; for though it will still be put to the question several times before its ultimate passage, yet I think if this day's vote of the Senate is favorable, it will pass safely through all the subsequent stages. It would have been a great comfort to me to have been near you during the preparation of this business of weights and measures. It is much easier to avoid errors by having good information at first, than to unravel and correct them after they are committed. I recommend to Congress the deferring to proceed on the report till the next session, and reserve to myself an opening to add any new matter which may occur in the meantime.
I am, with great and sincere esteem, dear Sir, your affectionate friend and servant.