WEIGHTS AND MEASURES. For the proper carrying on of mercantile transactions, and for many other purposes, it is nece-sary that there be fixed and readily accessible standards of magnitude, of weight, and of value. The lengths implied by the names a foot, e band, a cubit, a fittlona, are far too indefinite to have long continued to satisfy the wants of civilized nations; and in every country, by common consent, or by the action of government, determinate measures have been agreed upon. These masures, left almost to chance, have been different from one nation to another, even from county to county, sometimes from town to town, and still more awkwardly, often from one trade or guild to another.
Any one can appreciate the inconvenience of such a want of uniformity, for, in every transaction extending beyond his own sphere, he has to take account of the change Of measure, the change of weight, the change of money, perhaps of all three at once. We all see and allow that there ought to be only one system of weights and measures in one country; that one bushel in Winchester, another in New York—one acre in England, another in Scotland, and a third in Ireland; that troy weights, avoirdupois weights, and all the other local, conventional, and trade variations which abound in the British dominions, form an aggregate of unbearable confusion, leading to endless mistakes and ceaseless quarrels. It is not more difficult to extend our observation, and perceive that if one system be advisable for one country, a universal cosmopolitan system would be no less advantageous for the whole world.
The only practical method of establishing a system of measures is to construct stand ards of reference, and to preserve these carefully in some public place. In order that these standards may not be worn and injured by too frequent use, it is convenient to have authenticated copies deposited in the various towns, so that all dealers and arti ficers may have ready access to them, and so that all makers of weights and measures may be without excuse for errors in their workmanship.
To set up a standard of measure seems to be a very simple matter—the authorities have only to fix upon the proper length of a yard, to have a piece of wood or of metal made to that length, and to cause it to be properly marked and preserved. For common pur poses this seems to be quite enough: however, experience soon shows the inconvenience ' of this simple plan, for, by repeated contacts, the ends of the yard-measure get worn. Instead, therefore, of making a rod just a yard long, they make it a little longer, and upon it form two fine marks a yard distant from each other, and hold this distance to be the true standard. By this expedient the effects of wearing are got rid of; copy after copy can be compared with the original, without deterioration of the standard.
But use is not the only cause of deterioration: wood decays or is worm-eaten, and metals are liable to oxidation, so that the material has to be carefully chosen. This is not all. Every substance which has been examined is found to change its size with a change of temperature; the standard bar is shorter in winter than in summer, and the change, though it be so small as to be of no moment to the haberdasher, the Wright, or the mason, is enough to cause great trouble to those engaged in very accurate work. Hence, in the selection of the substance to be used for the standard bar, we must have an eye to smallness of expansion as well as to durability. The substances available, taken in the order of their expansibility, are: deal, glass, platinum, gold, silver, iron, brass, copper. Deal may be put aside as wanting in durability, and the choice may be said to lie between glass and platinum, neither of which is much acted on by the air, or by the vapors which are found in the atmospheres of large towns. The fragility of glass and the costliness of platinum are objections; but the latter is a mere trifle when a national standard is concerned. Platinum, then, seems to be the best substance.