STANDARD MEASURES AND WEIGHTS. Measures are wanted for two distinct objects, the commercial and the scien tific. The wants of natural philhsophy have grown up within the last two centuries ; while I so early as Magna Charta it was one of the concessions to the grievances of the subject, that there should be one weight and one measure throughout the land. But though a few acts of Parliament were sufficient, in pro cess of time, substantially to establish the po litical rights which that charter was intended to grant, hundreds of them, down to the pre sent time, have been ineffectual in producing the use of one weight and one measure. This unity was for commercial not scientific pur poses ; and the resemblance of natural objects was supposed to be a sufficient reliance for obtaining it. Some of the old statutes ex pressly make the inch to be the length of three barleycorns, placed end to end, romid and dry, from the middle of the ear. Stand ards were made no doubt from this definition ; or at least it was supposed that if the existing standard should be lost, the barleycorns would enable its restoration to be effected. The average length of three barleycorns, whether we call that length an inch or by any other name, among many thousands, would doubt less always be the same under similar condi tions of growth.
A commercial standard might be easily recovered from many different modes of pro ceeding : for example, the average height of the barometer at a given place throughout any period of five years is so nearly the same from one five years to another, that a com mercial standard might be sufficiently well obtained from it. It would be of little conse quence if the yard were wrongly recovered by one-hundredth or even one-tenth of an inch, in any matter of buying and selling.
It is the scientific standard at which the government has been aiming during the last century. The object here is, first, to measure the old standards to the utmost accuracy of which our senses, assisted by microscopes, are capable ; secondly, to discover the means of reconstructing a lost standard. In the more delicate operations of natural philosophy and astronomy, our knowledge cannot go down to posterity unless they know within the thousandth of an inch what it is that we call a yard. The public at largo has never understood the reason why so much trouble has been taken ; and perhaps the members of different administrations, while trusting such investigations to men of science, and relying on them for the whole conduct of the matter, may have wondered at the great diffi culty which there seemed to be in the way of furnishing the shopkeepers of all generations with yard measures and pound weights of the same values.
The following is the existing legal definition of standards according to the act of 1825: 1. The straight line or distance between the centres of the two points in the gold studs in the straight brass rod now in the custody of the clerk in the House of Commons, whereon the words and figures Standard yard, 1700' are engraved, shall be the original and genuine standard of that measure of length or lineal extension called a yard . . . the brass
being at the temperature of sixty-two degrees of Fahrenheit's thermometer. The act goes on in many words to say that the pendulum vibrating seconds of mean time in the latitude of London in a vacuum at the level of the sea is 39.1393 inches of the said standard.
2. The standard brass weight of one pound troy weight, made in the year 1758, now in the custody of the clerk of the House of Commons, shall be the original and genuine standard measure of weight The act goes on to say that the cubic inch of distilled water, weighed in air by brass weights, at 02° of Fahrenheit, the barometer being at 30 inches, is equal to 252•458 grains.
The last event in the history of this subject was the report (in 1841) of a commission of men of science appointed in 1838. After reciting that the standard yard was rendered absolutely useless by the fire at the House of Commons, and that the standard troy pound was altogether missing, the commissioners begin by recommending the total disuse of all attempts to procure a natural standard, and the return to the old plan of standards manu factured in metal ; that four copies of the best existing representations of the old stand ards should be made, and carefully compared ; that one of these copies should be hermeti cally sealed, and imbedded in the masonry of some public building, marked by an inscrip tion, and only to be opened by Act of Parlia ment ; that the standard of capacity be defined by that of weight, not by that of length ; that various precautions, minutely named, be taken for the preservation and Safe custody of the others; that the avoirdupois pound, and not the troy, be the standard ; that the govern ment purchase all the known copies of the old standards which have been noted in scientific operations ; that no circumstance would con tribute so much to the introduction of a decimal scale in weights and measures as the establishment of a decimal coinage, which is strongly recommended ; that the old Gunter's Chain be preserved in the measurement of land ; that a measure of 1,000 or 2,000 yards receive a name, and bo used co-ordinately with the mile, with a view to the gradual dis use of the latter; dm Steps have been taken to recover a standard yard, by comparison of the existing scales which had been compared with the last standard.
Although not directly of great importance to manufacturing and trading affairs, the determination of these standards is indirectly advantageous ; and the subject is at any rate worthy of more general public attention than it usually receives.