STANDARDS OF LENGTH, MASS AND TIME. Standards of length, mass and time are the fundamental units used alike in the business of daily affairs and in the measure ments and calculations of physical science.
The most important standards of length now used are the British yard and the international prototype metres. Both of these are legal stand ards in the United States, the metric system having been legalized in 1866. The relations of the yard and metre are shown by the following equations: 1 yard = 0.9143992 metres. 1 metre = 1.093614 yards. 1 metre = 3.28084.3 feet. 1 metre = 39.37011 inches.
The most important standards of mass now used are the British pound and the international prototype kilograms. Both are legal standards in the United States. The relations of the pound and kilogram are shown by the follow ing equations : 1 pound = 0.453592428 kilograms. 1 kilogram = 2.20462234 pounds.
The above relations of the yard and metre and the pound and kilogram are the precise values determined by the International Bure-tu of Weights and Measures. The relations which have been legalized. in the United States are: 1 metre = 39.37 inches.
1 kilogram = 2.2046 pounds.
The unit of time adopted by common cen sent, but used more especially in physical science, is the mean solar second, or 1-86400th part of the mean solar day. The minute, the hour, the day, etc., also in common use, are multiples of the mean solar second. The latter is derived, however, from the time of rotation of the earth, or from the interval between two successive transits of a fixed star across any meridian plane. This interval is called the sidereal day and it is equal in length to 86,164.1 mean solar seconds. The United States Bureau of Standards maintains fireproof vaults where platinum-iridium meter bars and kilogram weights are stored. This bureau makes tests of material for the use of the government, and conducts work looking to the maintenance of standards in all important industries. It has laboratories at Washington and Pittsburgh, and at the latter is the largest testing machine in the world. Consult 'Annual Reports, Bureau of Standards' (Washington, D. C.). See