THE METRIC SYSTEM. 319 



THE METRIC SYSTEM OF WEIGHTS AND MEASURES. 



By Professor A. E. KENNELLY, 



HARVARD UNIVERSITY. 



I~N this age the knowledge of arithmetic is so widespread that it is 

 -*- difficult to conceive that it is comparatively young. The three 

 R's, Reading, 'Riting and 'Rithmetic, seems to our mind almost 

 axiomatic and fundamental in regard to education. It is, therefore, 

 very interesting to read in histories of arithmetic that the earliest 

 known book which contains a systematic exposition of the decimal 

 system of numeration was written in the seventh century, and that 

 our familiar arabic numerals 1, 2, 3, 4, 5, 6, 7, 8, 9, can not be traced 

 to an earlier century than the seventh. According to Ball's ' Short 

 Account of the History of Mathematics,' the arabic arithmetic was 

 practically unknown in Europe until the end of the thirteenth cen- 

 tury. At that date numbers were written in Roman numerals. When 

 we see a date inscribed in Roman numerals upon the portal of a public 

 building, we witness the persistence, in art, of the system which was 

 in universal use for all the arithmetical purposes of the civilized world 

 only a few centuries ago. 



How simple to our minds to-day seems such a numerical problem 

 as a determination of the number of seconds in a mean solar day. 

 We write down the factors as 24X60X60, and in about twelve or 

 fifteen seconds, with pencil and paper, we arrive at the answer 86,400. 

 But how forbidding this problem would appear to us in the only form 

 known to our medieval ancestors, namely, XXIV. times LX. times 

 LX. How weary the way that would lead to the answer ! Is it any 

 wonder that the counting machine, or abacus, was largely used for the 

 simplest arithmetic; or that the expert arithmeticians in olden days 

 were known under the title of ' sweating calculators ' ? We read that 

 by the year 1400, the arabic numerals and simple arithmetic were 

 generally known throughout Europe, and were used in most scientific 

 and astronomical works. Most merchants continued, however, to keep 

 their accounts in Roman numerals until about 1550. That is to say, 

 unless history misinforms us, it took about a century and a half for 

 the simple arithmetic of arabic numerals to permeate from scientific 

 circles into the rank and file of the civilized nations. Looking back- 

 wards, this seems almost incredible. How was it possible for sensible 

 people to shut their eyes to the simplicity of a scientific rational sys- 

 tem of enumeration on the 1 2 3 ... 8 9 plan, and adhere to the 



