WEIGHTS AND MEASURES. THE study of Weights and Measures has now become one of the necessities as well as one of the accomplishments of the day. Those in common use are generally sufficiently well known for the ordinary purposes of the practitioner; but the day is not far distant when the French system will be so frequently employed, as the most convenient international standard, that the physician must be able to interpret it understandingly, if he wishes to keep abreast of the times in which he lives.1 The tables of weights and measures here given are almost wholly based on those published in the last edition (1873) of the U. S. Pharmacopoeia. ( 23 ) Relation of Weights and Measures of the U. S. Pharmacopoeia to each other. In distilled water at a temperature of 60°. Relation of Measures of the U. S. Pharmacopoeia to Cubic Weights and Measures of the Metrical System. The metric or metrical system is intended to secure uniformity throughout the world in all measurements of length, weight, and capacity. The units selected, the Metre, Gramme, and Litre, are defined in the following tables. As the great majority of practitioners regard the metric system as one of very recent introduction, it will be appropriate here to give a short sketch of its history, showing that, though only now becoming popularized in different countries of the world, it has been for many years a subject of agitation.' 1 This historical description and explanation of the metric system is taken from Photographic Mosaics, Philadelphia, 1877, article, Metric System, by H. A. Pintard. This system of weights and measures was first adopted in France. In the absence of any other natural standard it was determined, at the period of the first Revolution, to adopt an aliquot part of the terrestrial meridian; and in 1799 a provisional measure was adopted, supposed to be the ten millionth of the quadrant, or the forty millionth of the whole circumference measured over the poles. A commission of the Academy of Sciences, consisting of five of the most eminent mathematicians of EuropeBorda, Lagrange, Laplace, Monge, and Condorcet—were subsequently appointed, under a decree of the Constituent Assembly, to report upon the selection of a natural standard, and Delambre and Méchain were selected to measure an arc of the meridian between the parallel of Dunkirk and Barcelona. This labor was begun at the most agitated period of the Revolution, and accomplished only after many difficulties and dangers, as the astronomers and geometricians who carried on the operations were frequently molested, being taken for spies or enemies of France. The result was a wonderful approximation of the true length, the error being only about go of the length, or less in a single metre than go of an inch. By means of the arc of the meridian measured between Dunkirk and Barcelona, and of the arc measured in Peru, in 1736, by Bouguer and La Condamine, the length of the quarter of the meridian, or the distance from the pole to the equator, was calculated. This length was then divided into ten millions of equal parts, and one of these parts was taken for the unit of length, and called a metre, from the Greek word μirpov (a measure). The length of the metre as thus fixed is equal to 3.2808992 English feet, or very nearly 39.37079 English inches. From this unit of linear measure are derived all measures of length, surface, and solidity. The unit of long measure is therefore the metre, and from it is derived land measure, by calling 100 square metres an are. The are equals 3.955 English perches. : Liquid measure is obtained by making the unit or standard a litre, equal in capacity to a cubic decimetre = 0.2617 English gallon; dry measure, by making the standard a hectolitre 2 bushels and 3.35 pecks; while for solid measure the standard is a stere, equal to a cubic metre 35.317 cubic feet English. Lastly, to complete the series, weight is allied to the metre, by making the kilogramme to correspond with the contents of a cubic vessel of distilled water at the temperature of 4° C., or slightly above melting ice, the side of which cube is the tenth part of a metre (the decimetre), and the gramme to answer to the contents of a cubic vessel, the side of which is the hundredth part of the metre (the centimetre); for the contents of all cubic vessels are to each other in a triplicate ratio of their sides (Euclid, 33, xi.). All these units, by the prefixes, deca, deci, hecto, milli, etc., become applicable to any weights and measures, and, as the multiple of 10 connects all the larger and smaller measures, the whole becomes susceptible of decimal computation. No system of metrology hitherto invented can compare with this of the French in a scientific point of view, whilst its convenience for the purposes of commerce cannot fail to obtain its adoption by all civilized nations. The system was declared obligatory in France after November 2, 1801, and it has since been adopted in Spain, Belgium, Portugal, Holland, Greece, Sweden, Mexico, Brazil, and in 1868 was made compulsory in the German Empire. It was also legalized in Great Britain in 1864, and in 1866 an act was adopted by the Congress of the United States, making it lawful, after the passage of the act, throughout the United States, to employ the weights and measures of the metric system. Another act authorizes in post-offices the use of |