LXIV 
PHILOSOPHICAL SOCIETY OF WASHINGTON. 
varied considerably at different times and places, just as the modern 
pound has varied, but the relations stated are believed to have been 
the original ones. The ancient Chaldeans used not only the decimal 
system of notation, which is evidently the primitive one, but also a 
duodecimal system, as shown by the division of the year into twelve 
months, the equinoctial day and night each into twelve hours, the 
zodiac into twelve signs, etc., and a sexagesimal system by which 
the hour was divided into sixty minutes, the signs of the zodiac into 
thirty parts or degrees, and the circle into 360 degrees, wdth further 
sexagesimal subdivisions. The duodecimal and sexagesimal systems 
seem to have originated with the Chaldean astronomers, who, for 
some reason w^hich is not now evident, preferred them to the decimal 
system, and by the weight of their scientific authority impressed 
them upon their system of weights and measures. Now observe how 
closely the scientific thought of to-day repeats the scientific thought 
of four thousand years ago. These old Chaldeans took from the 
human body what they regarded as a suitable unit of length, and 
for their unit of mass they adopted a cube of water bearing simple 
relations to their unit of length. Four thousand years later, when 
these simple relations had been forgotten and impaired, some of the 
most eminent scientists of the last century again undertook the 
task of constructing a system of weights and measures. With them 
the duodecimal and sexagesimal systems were out of favor, while 
the decimal system was highly fashionable, and for that reason they 
subdivided their units decimally instead of duodecimally, sexagesi- 
mally, or by powers of two; but they reverted to the old Chaldean 
device for obtaining simple relations between their units of length 
and mass, and to that fact alone the French metric system owes its sur¬ 
vival. Every one now knows that the meter is not the ten millionth 
part of a quadrant of the earth’s meridian, and in mathematical 
physics, where the numbers are all so complicated that they can 
only be dealt with by the aid of logarithms, and the constant tt, an 
utterly irrational quantity, crops up in almost every integral, mere 
decimal subdivision of the units counts for very little. But in 
some departments of science, as, for example, chemistry, a simple 
relation’between the unit of length (which determines volume), the 
unit of mass, and the unit of specific gravity, is of prime impor¬ 
tance ; and wherever that is the case the metric system will be used. 
To engineers such relations are of small moment, and consequently 
among English-speaking engineers the metric system is making no 
