310 GEOLOGICAL EVIDENCES 
to exhibit their organisms, than we found that what they sub- 
mitted to our examination were tusks of the elephant and the 
mastodon, and bones of the rhinoceros, the ox, and the deer. 
If trees of the same dicotyledonous class as the plane and the 
buckthorn occurred in our Secondary or Paleozoic periods, in 
at least aught approaching to the recent or Tertiary propor- 
tions, how is it that amid their fossil woods, though they have 
yielded their specimens by thousands, not a single dicotyledon- 
ous specimen, save of the gymnosperme, has yet been found ? 
Or if the great Paleozoic period indeed abounded in mam- 
mals, such as the elephant and the deer, how is it that, while 
in the Paleozoic deposits of even our own neighborhood and 
country we have met with the remains of fishes by tens of 
thousands, and of molluses by millions, all the Paleozoic sys- 
tems of the world have hitherto failed to present us with a 
single mammalian tooth or bone? Or even if in these ancient 
deposits a few dicotyledonous woods or mammalian fragments 
were, after the search of years, to be found, what could we infer 
regarding the proportions in which either dicotyledons or mam- 
mals had existed in the periods which the deposits represented, 
save from the proportions in which we found their remains 
occurring in them? Nay, do we not find Sir Charles Lyell 
setting his imprimatur on an exactly similar style of induction 
as that upon which we found, when, in determining the various 
formations of the Tertiary division, he has recourse to his prin- 
ciple of per centages? He would assuredly not deem that 
a Pliocene or Miocene deposit among whose numerous organ- 
isms he had failed to find an existing plant or shell. In the 
geologic, as in other departments, 
““ What can we reason but from what we know.” 
The gulf between mental and geologic science is still too 
broad, and perhaps too carelessly surveyed on the theologic 
