For measures of capacity, wet and dry,
To incorporate into the same system our weights and coins, we must recur to some natural substance, to be found everywhere, and of a composition sufficiently uniform. Water has been considered as the most eligible substance, and rain-water more nearly uniform than any other kind found in nature. That circumstance renders it preferable to distilled water, and its variations in weight may be called insensible.
The cubic unit of this = .1 would weigh about 2,165 lbs. or a ton between the long and short.
With respect to our coins, the pure silver in a dollar being fixed by law at 347¼ grains, and all debts and contracts being bottomed on that value, we can only state the pure silver in the dollar, which would be very nearly 23 millionths.
I have used loose and round numbers (the exact unit being yet undetermined) merely to give a general idea of the measures and weights proposed, when compared with those we now use. And in the names of the subdivisions I have followed the metrology of the ordinance of Congress of 1786, which for their series below unit adopted the Roman numerals. For that above unit the Grecian is convenient, and has been adopted in the new French system.
We come now to our last question, in what form shall we offer this metrical system to the world? In some one which shall be altogether unassuming; which shall not have the appearance of taking the lead among our sister institutions in making a general proposition. So jealous is the spirit of equality in the republic of letters, that the smallest excitement of that would mar our views, however salutary for all. We are in habits of correspondence with some of these institutions, and identity of character and of object, authorize our entering into correspondence with all. Let us then mature our system as far as can be done at present, by ascertaining the length of the second pendulum of 45° by forming two tables, one of which shall give the equivalent of every different denomination of measures, weights and coins in these States, in the unit of that pendulum, its decimals and multiples; and the other stating the equivalent of all the decimal parts and multiples of that pendulum, in the several denominations of measures, weights and coins of our existing system. This done, we might communicate to one or more of these institutions in every civilized country a copy of those tables, stating as our motive, the difficulty we had experienced, and often the impossibility of ascertaining the value of the measures, weights and coins of other countries, expressed in any standard which we possess; that desirous of being relieved from this, and of obtaining information which could be relied on for the purposes of science, as well as of business, we had concluded to ask it from the learned societies of other nations, who are especially qualified to give it with the requisite accuracy; that in making this request we had thought it our duty first to do ourselves, and to offer to others, what we meant to ask from them, by stating the value of our own measures, weights and coins, in some unit of measure already possessed, or easily obtainable, by all nations; that the pendulum vibrating seconds of mean time, presents itself as such an unit; its length being determined by the laws of nature, and easily ascertainable at all times and places; that we have thought that of 45° would be the most unexceptionable, as being a mean of all other parallels, and open to actual trial in both hemispheres. In this, therefore, as an unit, and in its parts and multiples in the decimal ratio, we have expressed, in the tables communicated, the value of all the measures, weights and coins used in the United States, and we ask in return from their body a table of the weights, measures and coins in use within their country, expressed in the parts and multiples of the same unit. Having requested the same favor from the learned societies of other nations, our object is, with their assistance, to place within the reach of our fellow citizens at large a perfect knowledge of the measures, weights and coins of the countries with which they have commercial or friendly intercourse; and should the societies of other countries interchange their respective tables, the learned will be in possession of an uniform language in measures, weights and coins, which may with time become useful to other descriptions of their citizens, and even to their governments. This, however, will rest with their pleasure, not presuming, in the present proposition, to extend our views beyond the limits of our own nation. I offer this sketch merely as the outline of the kind of communication which I should hope would excite no jealousy or repugnance.
Peculiar circumstances, however, would require letters of a more special character to the Institute of France, and the Royal Society of England. The magnificent work which France has executed in the admeasurement of so large a portion of the meridian, has a claim to great respect in our reference to it. We should only ask a communication of their metrical system, expressed in equivalent values of the second pendulum of 45° as ascertained by Messrs. Borda, Coulomb and Cassini, adding, perhaps, the request of an actual rod of the length of that pendulum.
With England, our explanations will be much more delicate. They are the older country, the mother country, more advanced in the arts and sciences, possessing more wealth and leisure for their improvement, and animated by a pride more than laudable.1 It is their measures, too, which we undertake to ascertain and communicate to themselves. The subject should therefore be opened to them with infinite tenderness and respect, and in some way which might give them due place in its agency. The parallel of 45° being within our latitude and not within theirs, the actual experiments under that would be of course assignable to us. But as a corrective, I would propose that they should ascertain the length of the pendulum vibrating seconds in the city of London, or at the observatory of Greenwich, while we should do the same in an equidistant parallel to the south of 45°, suppose in 38° 29´. We might ask of them, too, as they are in possession of the standards of Guildhall, of which we can have but an unauthentic account, to make the actual application of those standards to the pendulum when ascertained. The operation we should undertake under the 45th parallel, (about Passamaquoddy,) would give us a happy occasion, too, of engaging our sister society of Boston in our views, by referring to them the execution of that part of the work. For that of 38° 29´ we should be at a loss. It crosses the tide waters of the Potomac, about Dumfries, and I do not know what our resources there would be unless we borrow them from Washington, where there are competent persons.
Although I have not mentioned Philadelphia in these operations, I by no means propose to relinquish the benefit of observations to be made there. Her science and perfection in the arts would be a valuable corrective to the less perfect state of them in the other places of observation. Indeed, it is to be wished that Philadelphia could be made the point of observation south of 45°, and that the Royal Society would undertake the counterpoint on the north, which would be somewhere between the Lizard and Falmouth. The actual pendulums from both of our points of observation, and not merely the measures of them, should be delivered to the Philosophical Society, to be measured under their eye and direction.
As this is really a work of common and equal interest to England and the United States, perhaps it would be still more respectful to make our proposition to her Royal Society in the outset, and to agree with them on a partition of the work. In this case, any commencement of actual experiments on our part should be provisional only, and preparatory to the ultimate results. We might, in the meantime, provisionally also, form a table adapted to the length of the pendulum of 45°, according to the most approved estimates, including those of the French commissioners. This would serve to introduce the subject to the foreign societies, in the way before proposed, reserving to ourselves the charge of communicating to them a more perfect one, when that shall have been completed.
We may even go a step further, and make a general table of the measures, weights and coins of all nations, taking their value hypothetically for the present, from the tables in the commercial dictionary of the encyclopedia methodique, which are very extensive, and have the appearance of being made with great labor and exactness. To these I expect we must in the end recur, as a supplement for the measures which we may fail to obtain from other countries directly. Their reference is to the foot or inch of Paris, as a standard, which we may convert into parts of the second pendulum of 45°.
I have thus, my dear sir, committed to writing my general ideas on this subject, the more freely as they are intended merely as suggestions for consideration. It is not probable they