26 THE REALITIES OF MODERN SCIENCE 



The standards would sometimes be lost or destroyed, 

 and then a new unit would have to be chosen. Per- 

 haps the new unit was made practically of the same 

 length as the old by reference to the walls of some 

 building for which people remembered the lengths 

 as expressed in the former unit. At any rate it is by 

 this method that archeologists to-day obtain their 

 ideas as to the length of the units used in ancient times. 



Other units may be formed by taking multiples and 

 submultiples of the adopted unit. This is also the custom 

 to-day in the case of the so-called metric units, of which 

 the meter is the unit of length. The multiple unit which 

 occurs most frequently is formed by the prefix "kilo, " 

 meaning "one thousand." The submultiples are 

 formed by using Latin prefixes instead of Greek, thus 

 "centi" and "milli" for "one hundredth" and "one 

 thousandth." 



Different localities had different units, although there 

 was a tendency toward the reduction of the number of 

 units, due to the formation of large empires and to the 

 usages of traders. Such a standardization ultimately 

 resulted in greater simplicity and facilitated trade, 

 for we all recognize the inconvenience attaching to 

 the use of different systems, e.g. metric and English. 

 The tendency to standardize was most marked in the 

 case of units of weight. If money is to perform its 

 proper service in the exchange of goods, then each piece 

 of a given denomination must be as nearly as possible 

 the same as any other. It was somewhat, probably, 

 to insure the full payment of taxes and for reasons 

 of pride, but largely to stabilize trade, that monarchs 

 were especially concerned with weights and measures. 



