FUNDAMENTAL UNITS OF MEASURE. 139 



is possible, and the multii^les aud sub-multiples should be so related to 

 them that units of every possible dimension and character for conven- 

 ience in the measurement of all measureable things may be derived 

 from them in the simplest manner, and thus be capable of the easiest 

 reduction and interchange. The units of length, mass, and time, as 

 represented by the centimeter, the gram and the second, fulfill these 

 requirements almost as perfectly as possible. The second falls short 

 of the others because its multiples are not decimally derived, but its 

 use is and has long been so nearly universal that it is not likely to be 

 modified in that respect in the near future. Indeed, a decimal system 

 as applied to time is much less important than when considered in rela- 

 tion to length and mass. 



As to the constancy of these units, an arbitrary length and an arbi- 

 trary mass are much more capable of accurate reproduction than any 

 natural units of which we now know. When reproduced in considera- 

 ble numbers and of the best known material, aud when widely dis- 

 tributed throughout the civilized world as they now are, under the direc- 

 tion of the International Bureau of Weights and Measures, anything- 

 like destruction or loss of the standards must be regarded as well-nigh 

 impossible. Copied in materials of various kinds and preserved under 

 conditions widely varying, it is hardly likely that any secular change 

 in the standards can escape detection, and the accurate determination 

 of the meter in light waves now in i^rogress will aflbrd a valuable check 

 on the constancy of the standard of length. 



It thus appears that the metric system with its derived units is to day 

 by far the most perfect system of metrology ever used by man, and 

 that it lacks little of theoretical perfection. It can hardly be denied 

 that in one or two matters of minor importance it is susceptible of 

 improvement, but it possesses the inestimable and unapproachable 

 advantage of being actually in use by the great majority of civilized 

 nations. Among the innumerable metrological schemes which have 

 made their appearance within the past one hundred years, it is quite 

 jiossible that some one of them possesses advantages over that based on 

 the meter and the kilogram, and that it would be preferred if we were 

 starting afresh with the whole question. But we are not starting- 

 afresh, and it is certainly a cause for sincere and earnest congratula- 

 tion that a system which is so rapidly advancing in public favor is as 

 nearly absolutely perfect as is this. 



Let us turn now to a brief consideration of the origin and i)resent 

 condition of what Lord Kelvin has justly characterized as the brain- 

 wearying, intellect-destroying- system of weights and measures in use 

 among English-speaking people. 



The fundamental unit of length is the yard, and the unit of mass is 

 the pound. In the time of Edward II it was enacted (A. d. 1324) that 

 3 barleycorns, round and dry, should make 1 inch and 12 inches make 

 1 foot. The earliest actual material standard yard of which there is 



