LETTER CXXVIII.—TO MR. RUTHERFORD, December 25, 1792
TO MR. RUTHERFORD.
Philadelphia, December 25, 1792.
Sir,
I have considered with all the attention which the shortness of the time would permit, the two motions which you were pleased to put into my hands yesterday afternoon, on the subject of weights and measures, now under reference to a committee of the Senate, and will take the liberty of making a few observations thereon.
The first, I presume, is intended as a basis for the adoption of that alternative of the report on measures and weights, which proposed retaining the present system, and fixing its several parts by a reference to a rod vibrating seconds, under the circumstances therein explained: and to fulfil its object, I think the resolutions there proposed should be followed by this; ‘that the standard by which the said measures of length, surface, and capacity shall be fixed, shall be an uniform cylindrical rod of iron, of such length, as in latitude forty-five degrees, in the level of the ocean, and in a cellar or other place of uniform natural temperature, shall perform its vibrations in small and equal arcs, in one second of mean time, and that rain-water be the substance, to some definite mass of which the said weights shall be referred.’ Without this, the committee employed to prepare a bill on those resolutions, would be uninstructed as to the principle by which the Senate mean to fix their measures of length, and the substance by which they will fix their weights.
The second motion is a middle proposition between the first and the last alternatives in the report. It agrees with the first in some of the present measures and weights, and with the last, in compounding and dividing them decimally. If this should be thought best, I take the liberty of proposing the following alterations of these resolutions.
2nd. For ‘metal’ substitute ‘iron.’ The object is to have one determinate standard. But the different metals having different degrees of expansibility, there would be as many different standards as there are metals, were that generic term to be used. A specific one seems preferable, and ‘iron ‘the best, because the least variable by expansion.
3rd. I should think it better to omit the chain of 66 feet, because it introduces a series which is not decimal, viz. 1. 66. 80. and because it is absolutely useless. As a measure of length, it is unknown to the mass of our citizens; and if retained for the purpose of superficial measure, the foot will supply its place, and fix the acre as in the fourth resolution.
4th. For the same reason I propose to omit the words ‘or shall be ten chains in length and one in breadth.’
5th. This resolution would stand better, if it omitted the words ‘shall be one foot square, and one foot and twenty cents of a foot deep, and,’ because the second description is perfect, and too plain to need explanation. Or if the first expression be preferred, the second may be omitted, as perfectly tautologous.
6th. I propose to leave out the words ‘shall be equal to the pound avoirdupois now in use, and,’ for the reasons suggested on the second resolution, to wit, that our object is, to have one determinate standard. The pound avoirdupois now in use, is an indefinite thing. The committee of parliament reported variations among the standard weights of the exchequer. Different persons weighing the cubic foot of water have made it, some more and some less than one thousand ounces avoirdupois; according as their weights had been tested by the lighter or heavier standard weights of the exchequer. If the pound now in use be declared a standard, as well as the weight of sixteen thousand cubic cents of a foot in water, it may hereafter, perhaps, be insisted that these two definitions are different, and that being of equal authority, either may be used, and so the standard pound be rendered as uncertain as at present.
7th. For the same reasons I propose to omit the words ‘equal to seven grains troy.’ The true ratio between the avoirdupois and troy weights, is a very contested one. The equation of seven thousand grains troy to the pound avoirdupois, is only one of several opinions, and is indebted perhaps to its integral form for its prevalence. The introduction either of the troy or avoirdupois weight into the definition of our unit, will throw that unit under the uncertainties now enveloping the troy and avoirdupois weights.
When the House of Representatives were pleased to refer to me the subject of weights and measures, I was uninformed as to the hypothesis on which I was to take it up; to wit, whether on that, that our citizens would not approve of any material change in the present system, or on the other, that they were ripe for a complete reformation. I therefore proposed plans for each alternative. In contemplating these, I had occasion to examine well all the middle ground between the two, and among others which presented themselves to my mind, was the plan of establishing one of the known weights and measures as the unit in each class; to wit, in the measures of lines, of surfaces, and of solids, and in weights, and to compound and divide them decimally. In the measure of weights, I had thought of the ounce as the best unit, because, calling it the thousandth part of a cubic foot of water, it fell into the decimal series, formed a happy link of connection with the system of measures on the one side, and of coins on the other, by admitting an equality with the dollar, without changing the value of that or its alloy materially. But on the whole, I abandon this middle proposition, on the supposition that if our fellow-citizens were ripe for advancing so great a length towards reformation, as to retain only four known points of the very numerous series to which they were habituated, to wit, the foot, the acre, the bushel, and the ounce, abandoning all the multiples and subdivisions of them, or recurring for their value to the tables which would be formed, they would probably be ripe for taking the whole step, giving up these four points also, and making the reformation complete; and the rather, as in the present series and the one to be proposed, there would be so many points of very near approximation, as, aided in the same manner by tables, would not increase their difficulties, perhaps, indeed, would lessen them by the greater simplicity of the links by which the several members of the system are connected together. Perhaps, however, I was wrong in this supposition. The representatives of the people in Congress are alone competent to judge of the general disposition of the people, and to what precise point of reformation they are ready to go. On this, therefore, I do not presume to give an opinion, nor to pronounce between the comparative expediency of the three propositions; but shall be ready to give whatever aid I can to any of them which shall be adopted by the legislature.
I have the honor to be, with perfect respect, your most obedient and most humble servant,
Th: Jefferson.