“ 36-- ^pouces 8.52. ^lignes this is 1/10 of a line less than S ^r. I. Newton’s, and the Bishop accordingly adds that there may be in this calculation an error of 1/10 of a line.

" I had taken no notice of the precaution of making the experiment of the pendulum on the sea-shore, because the highest mountain in the U. S. would not add 1/5000 part to the length of the earth’s radius, nor 1/128 of an inch to the length of the pendulum; the highest part of the Andes indeed might add about 1/1000 to the Earth’s radius, & 1/25 of an inch to the pendulum. as it has been thought worth mention, I will insert it also . . . ”

Jefferson sent his revised report to Rittenhouse on June 17th: “ I now inclose you the alterations of my report which were rendered necessary by the bishop of Autun’s plan. those in the first four pages being numerous, I wrote those pages anew, so that you will be so good as to substitute the new for the old. I have only noted the other smaller alterations by the page & line . . . ”

Three days later he again wrote to Rittenhouse: “ I inclosed you on the 17 ^th. the alterations I had made in my report in consequence of the B ^p. of Autun’s proposition which had come to my hands two days before. on the 18 ^th. I received from m ( ^~ r) Cutting in London a packet of newspapers, among which were the two inclosed, containing the speech in parliament of S ^r John Riggs Miller on the subject of weights and measures. I observe he states the estimate of 39.2 I. for the length of the pendulum as confessedly erroneous. I had adopted it from memory only and before I had been able to get a single book of any kind in the 1 ^st. part of the report, wherein I endeavor to ascertain and fix invariably the system of measures & weights now in use with us. but before I proceeded to the 2 ^d. part, proposing a thorough reform and the reducing the whole to the decimal ratio, I had been able to procure here a copy of the Principia, and so to recur to the fountain head for S ^r. I. Newton’s calculation: and then added the note, which you will find page 3. of the report . . . all which I submit to your judgment, and I will ask you particularly to examine the numbers .0112 and .019 as I have no help here to find them otherwise than by approximation. I have wished much, but in vain, to find Emerson’s & Ferguson’s books here. in short I never was cut off from the resources of my own books & papers at so unlucky a moment. there is a Count Andriani of Milan here, who sais there is a work on the subject of weights & measures published by Frisi of Milan. perhaps you may have it at Philadelphia, & be able to send it to me. were it not for my confidence in your assistance I should not have ventured to take up this business till I recieve my books . . . ”

On June 21 Rittenhouse wrote to Jefferson a long letter of critical comment on the report, beginning: “I received yours of the 12 ^th. 14 ^th. and 17 ^th. together with the several papers mentioned, to which I shall give as much attention, and as soon as my health will permit. In the mean time I thought it not amiss to transmit to you such observations as occurred to me on first reading them.

"I am not quite satisfied with the reasons given (page 1.) for having recourse to motion for a Standard of measure. The true reason seems to be, not because all matter is variable in its dimensions, for that is a difficulty we have to contend with after recourse is had to the motion of pendulums, but because a Standard rod of any given length may be irrecoverably lost, and because no such rod has been preserved for us from ancient times, nor can we undertake to transmit them to posterity with sufficient authenticity, or to different Countries for general use . . .”

To Rittenhouse’s letter of the 21st, Jefferson replied from New York on June 26th: “ Your favor of the 21 ^st. came duly to hand, and I admit all your corrections with great thankfulness. the first was an inaccuracy of expression. I meant to say that there existed not in nature any one species of body or thing, such as a digit, palm, span, foot, cubit, barley corn &c. which furnished us with a constant uniform dimension. I have corrected it accordingly. the statement of the expansion of the rod was an error in having multiplied the number only once, instead of twice, by 12. I have stated in a note the reason for continuing the double expressions, and having now made the other corrections, all of which fell within the first sheet, I ”