Probably no profession would benefit to a greater extent by the introduction of the metric system in the United States and Great Britain than would that of mining-engineering. This is eminently an international science, and to maintain a place in the first rank of his profes sion the mining engineer must keep himself constantly informed as to the latest methods and improvements introduced in foreign lands. Wherever the metric system is employed, all the data on this profession are expressed in metric weights and measures. When, however, the United States engineer wishes to use these data in connection with his own work, or to compare them with those recording native methods and machinery, he is forced to make a number of very tedious calculations before he can arrive at any exact comparisons. An approximate idea he may indeed quickly, gain, but in any exact science all mere approximations are prac tically useless.
The metric system has for some time been in exclusive use in the medical department of the United States army, and with the entry of the United States into the war against the Cen tral empires, it was used in the manufacture of certain sizes of guns, notably in those conform ing to the famous French "75's,* the 75-milli meter guns that have proved their superiority to the other field artillery of similar size and also of the 105 millimeter and the 155 milli meter guns. The General Chief of Staff wrote in January 1918, that it was followed in the preparation of operation orders and in man construction for the troops in France, as well as for firing data for artillery and machine guns to be used there. The artillery and ma chine gun material intended for service abroad was modified to conform with metric measure ments.
Another step in furtherance of the adoption of the metric system is one that has recently been taken in the gem-dealers' industry. This concerns the adoption, in precious stone com merce, of an international metric carat of 200 milligrams, to take the place of the various and discrepant national carat-weights that have for so long been sources of serious annoyance, in convenience and loss of time for gem-dealers. In a paper read in Chicago before the Interna tional Congress of Weights and Measures, held in connection with the Worlds' Colum bian Exposition of 1893, the writer suggested dividing the carat into 100 parts, and constitut ing a standard international carat of 200 milli grams, that is, 5 carats, or 20 pearl grains, to a French gram. This represented a deprecia tion in weight of only about 2% per cent from the carat-weights most in use. Great credit for
definitely initiated this much-needed re form is unquestionably due to M. C. E. Guil laume, Director of the Bureau international des Folds et Mesures at S4vres, who energetically and successfully advocated the reform in 1906 before the Commission des Instruments et Tra vaux, in Paris.* Simplicity of the Metric System.— There is only one system of: weights and measures in the world by means of which, if a voyager were wrecked on a desert island with only one meas ure, and that so small that it could be put in a lady's thimble, he could reconstruct all the measures for distance, for weight and for capacity, could map out the island, weigh up to tons and know the capacity of any receptacles he might construct. That system is the metric system, and that measure is the cubic centi meter, made hollow, and graduated on the edge in millimeters.
Having this, he could mark a stick up to a meter, dividing it into decimeters, centimeters and millimeters. This meter multiplied a thou sand times would give him the kilometer — the standard measure of distance. It would also enable him to determine how many square meters the island measured, and hence how many ares (100 square meters) and hectares (10,000 square meters) it covered in area. Or, he could fill the cubic centimeter with water, which would weigh one gram, and multiplying this by a thousand would give him a kilogram, the standard measure of weight. The cubic centimeter would hold one milliliter of water and 1,000 milliliters would give him the liter, the standard measure of capacity.
The meter for the unit of length, the liter for the unit of capacity and the gram for the unit of mass or weight is the sum and sub stance of the metric system. These three units (meter, liter, ?ram) with the following divi sions and multiples are winning their way into general use because they are best suited for practical purposes.
The prefixes from the Latin, milli; centi; deci; representing respectively a thousandth, a hundredth and a tenth, and those from the Greek, deka, hecto and kilo representing respec tively 10, 100 and 1,000 may be used with any of the metric units. Investigation and experience in the United States and in metric countries, however, indicate the desir ability of holding to the metric weights and measures given in the foregoing table, as these are considered sufficient and best for profes sional work, the industries and trade. Ten meters, for-instance, is briefer and more read ily understood than one dekameter.