TO THOMAS COOPER, ESQ.

Washington, October 27, 1808.

Dear Sir,—When I received your letter of the 16th, I thought I had not a copy of my report on measures, weights, and coins, except one bound up in a volume with other reports; but on carefully searching a bundle of duplicates, I found the one I now enclose you, being the only detached one I possess. It is defective in one article. The report was composed under a severe attack of periodical headache, which came on every day at sunrise, and never left me till sunset. What had been ruminated in the day under a paroxysm of the most excruciating pain, was committed to paper by candlelight, and then the calculations were made. After delivering in the report, it was discovered that in calculating the money unit § 5 page 49, there was a small error in the third or fourth column of decimals, the correction of which however brought the proposed unit still nearer to the established one. I reported the correction in a single leaf to Congress. The copy I send you has not that leaf.

The first question to be decided is between those who are for units of measures, weights, and coins, having, a known relation to something in nature of fixed dimension, and those who are for an arbitrary standard. On this "dice vexata quaestio" it is useless to say a word, every one having made up his mind on a view of all that can be said. Mr. Dorsey was so kind as to send me his pamphlet, by which I found he was for the arbitrary standard of one-third of the standard yard of H. G. of England, supposed to be in the Exchequer of that nation, a fac simile of which was to be procured and lodged in Philadelphia. I confess myself to be of the other sect, and to prefer an unit bearing a given relation to some fixed subject of nature, and of preference to the pendulum, because it may be in the possession of every man, so that he may verify his measures for himself. You will observe that I proposed alternative plans to Congress, that they might take the one or the other, according to the degree of courage they felt. The first is from page 18 to 38; the second from page 39 to 44. Were I now to decide, it would be in favor of the first, with this single addition, that each of the denominations there adopted, should be divisible decimally at the will of every individual. The iron-founder deals in tons; let him take the ton for his unit, and divide it into 10ths, 100ths, and 1000ths. The dry-goods merchant deals in pounds and yards; let him divide them decimally. The land-measurer deals in miles and poles; divide them decimally, only noting over his figures what the unit is, thus:

Tons.Lbs.Yds.Miles.
18.943,18.943,1.8943,189.43,&c.

I have lately had a proof how familiar this division into dimes, cents, and mills, is to the people when transferred from their money to anything else. I have an odometer fixed to my carriage, which gives the distances in miles, dimes, and cents. The people on the road inquire with curiosity what exact distance I have found from such a place to such a place; I answer, so many miles, so many cents. I find they universally and at once form a perfect idea of the relation of the cent to the mile as an unit. They would do the same as to yards of cloth, pounds of shot, ounces of silver, or of medicine. I believe, therefore, they are susceptible of this degree of approximation to a standard rigorously philosophical; beyond this I might doubt. However, on this too every one has an opinion, and I am open to compromise, as I am also to other plans of reformation, of which multitudes have been published. I can conclude, therefore, candidly with the "si quid novisti rectius," &c., and sincerely with assurances of my constant esteem and respect.