THE 
AMERICAN GEOLOGIST 
Vou. IX. JANUARY, 1892. No. lL. 
JOSEPH LEIDY, M.D., LL.D. 
By Prenrsrror FrRAzer, Philadelphia. 
There is no more striking ditference between the past and present 
generations of scientific men than the universality of the knowl- 
edge of the greatest men of the past and the absence of any pre- 
tension to it in our present representatives. It could not be other- 
wise. In classic times as well as in the middle ages the distinc- 
tion between words and things was not always clearly made. The 
same class of mind which would successfully grapple with the 
paradoxes of the schoolmen was equally serviceable in speculations 
on the philosopher's stone, the existence of phlogiston, or the inter- 
pretation of a Greek text. Words were all important, the methods 
of logic were conventional, and no extraordinary memory was re- 
quired to master at least in outline all that man had attained; 
while the discussion of this knowledge could always be turned into: 
the channel of the then philosophy, after which the battle was en- 
tirely with words and a skillful word-fencer could never be silenced 
however little progress he made in convincing his opponent. 
With the closing half of the last century, however, methods 
were improved, the number of facts increased in geometrical pro- 
gression with the years, and out of chaos and clamor, orderly 
classification and definite shapes were evoloved, each one requir- 
ing a different interpretation, claiming different classes of men, 
and requiring different instruments of precision. As the paths of 
research diverged it became more and more difficult for any one: 
man to understand all the regions through which they passed, andi 
one by one the philosophers became specialists. [In the early 
part of this century the enormous development of natural and ex- 
