craggy mountains, would admit; that all the calculations have been free of error, their coincidences faithfully reported, and that, whether in peace or war, to foes as well as friends, free access to the original will at all times be admitted. In favor of the standard to be taken from the time employed in a revolution of the earth on its axis, it may be urged that this revolution is a matter of fact present to all the world, that its division into seconds of time is known and received by all the world, that the length of a pendulum vibrating seconds in the different circles of latitude is already known to all, and can at any time and in any place be ascertained by any nation or individual, and inferred by known laws from their own to the medium latitude of 45°, whenever any doubt may make this desirable; and that this is the particular standard which has at different times been contemplated and desired[1] by the philosophers of every nation, and even by those of France, except at the particular moment when this change was suddenly proposed and adopted, and under circumstances peculiar to the history of the moment. But the cogent reason which will decide the fate of whatever you report is, that England has lately adopted the reference of its measures to the pendulum. It is the mercantile part of our community which will have most to do in this innovation; it is that which having command of all the presses can make the loudest outcry, and you know their identification with English regulations, practices, and prejudices. It is from this identification alone you can hope to be permitted to adopt even the English reference to a pendulum. But the English proposition goes only to say what proportion their measures bear to the second pendulum of their own latitude, and not at all to change their unit, or to reduce into any simple order the chaos of their weights and measures. That would be innovation, and innovation there is heresy and treason. Whether the Senate meant more than this I do not know; and much doubt if more can be effected. However, in endeavors to improve our situation, we should never despair; and I sincerely wish you may be able to rally us to either standard, and to give us an unit, the aliquot part of something invariable which may be applied simply and conveniently to our measures, weights, and coins, and most especially that the decimal divisions may pervade the whole. The convenience of this in our monied system has been approved by all, and France has followed the example. The volume of tracts which you have noted in the library of Congress, contains everything which I had then been able to collect on this subject. You will find some details which may be of use in two thin 4to vols., Nos. 399, 400, of chapter xxiv.; the latter being a collection of sheets selected from the "_Encyclopedie Methodique_," on the weights, measures and coins of all nations, bound up together and alone; and the former a supplement by Beyerlé. Cooper's