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.