466 



THE METEIC SYSTEM OF 



hereby, authorized and directed to furnish to the post offices exchanging mails 

 with foreign countries, and to such other offices as he shall think expedient, 

 •postal balances denominated in grams, of the metric system, and until otherwise 

 provided by law, one-half ounce avoirdupois shall be deemed and taken for pos- 

 tal purposes as the equivalent of fifteen grams of the metric weights, and so 

 adopted in progression ; and the rates of postage shall be applied accordingly. 



The metric system is so called from the metre, which is its principal and only 

 arbitrary unit. It is in use, to the exclusion of other weights and measures, in 

 several countries of Europe, and is in partial use in almost all the nations of 

 Christendom. 



UNITS OF THE SYSTEM. 



The metre is a measure of length. It is intended to be, and is very nearly, 

 one ten-millionth part of the distance from the equator to the pole, measured on 

 the earth's surface. • It is 39.37 inches, very nearly. Five metres are a little 

 less than a rod. 



The arc is a measure of surface, and is equal to a sqiiare whose side is 10 

 metres. It contains 100 square metres, or a little less than four square rods. 



The litre is the unit of dry measure, and also of liquid measure. It is equal 

 to the volume of a cube whose edge is one tenth of a metre. A cubic metre, 

 therefore, contains 1,000 litres. The litre is a little more than a wine quart, 

 being equal to about IjL- quart. 



The gram is the unit of weight, and is the weight of a cube of water, each 

 edge of the cube being y^ of a metre. A litre of water weighs, therefore, 1,000 

 gi-ams, and a cubic metre of water weighs 1,000,000 grams. A gram is 15.432 

 + grains. 



The store is a cubic metre, and is about 1.308 cubic yards. 



Each of these units is divided decimally, and also 1 ivger unit^ are formed from 

 multiples by 10, 100, 1,000, &cc. The successive multiples are designated by 

 the prefixes dcka, hecto, kilo and myria / the successive parts by deci, ctnti, and 

 milli. 



The following schedules of equivalents of the several units of the system rep- 

 resent their values in denominations in ut-o. The numbers are not carried to the 

 highest degree of accuracy, but the amount uf the error in them is generally 

 (except in some of the smaller denomiantions) less than the change due to a 

 cli£ference of two or three degrees of temperature of the standard metre bar. 



Weasures of length. 



METRIC DEXOMINATIOXS AND VALUES. 



EQUIVALENTS IN DENOMINATIONS IN USE. 



llyriametre . 

 Kilometre- .. 

 Hectomt-tie . 

 Decametre . . 



Metre 



Decimetre. .. 

 Centimetre .. 

 Millimetre. .. 



10, 000 metres 



1,000 metres 



100 metres 



10 metres 



1 metre 



jQ th of a metre 



TuTitli of a metre 



yfr(_urtli of a metre 



6.2137 mile.s. 



0.6-2 1:17 mile, or 3,230 feet aud 10 inches. 



323 felt aud one iuch. 



393.7 inches. 



39.37 inches. 



3.937 inches. 



0.3937 iuch. 



0.0394 inch. 



