88 
THE SCIENTIST. 
the moutlis of creeks or rivers where 
salt uiul fresh waters come in contact 
and are united. There are mixny species 
that are nsually assigned to such waters. 
Among them may be mentioned the dif- 
ferent species of myalina. 
By a careful study of fossils and other 
organic remains in situ, it is possible 
to determine the directions of the cur- 
rents, if any entered, as vehicles, in their 
deposition. 
11. Index To Climate. 
By t]ii^3 means preliistoric and extinct 
rivers and other bodies of water may be 
outlined and determined with a high 
degree of confidence in the conclusions 
reached. 
As before intimated, fossils afford an 
index to the climate of the geological 
ages of the past. From them it is pos- 
sible to determine, or at least approx- 
imate, the degree of temperature and 
moisture present and prevailing at the 
time they were endowed witli life. They 
also indicate the presence or absence of 
]iL!:ht thtit was associated with their other 
life conditions'. 
2. Fossils indicate the climatic changes 
of a given locality. A series of rocks, 
with the fossils the}" contain, may indi- 
cate the intense cold of the glacial epoch. 
OtliGr rocks and fossils in the same 
neighborhood may indicate that they are 
a result of the warm carboniferous clim- 
ate — peculiar to the coal age or even of 
the intense heat that gave character to 
the igneous rocks, e. g., the mamm(>th, 
etc. in Siberia. 
III. Index to Historical ZooloCtY 
AND Botany. 
1. By a comparison of the ditferent 
types of plauts and animals, os preserved 
in the rocks, a comprehensive view of 
these subjects may be had. When com- 
pared, or contrasted, with present types 
and standards, conclusions can be reach- 
ed regarding the evolution, progression 
or retrogression of species. By such com- 
parisons, we conclude that sjme orders 
aud genera have clianged rapidly in their 
comprehensive types, while others have 
remained almost permanent and fixed 
for untold ages. As examples of the for- 
mer, take the ostrea and the equista. The 
raodern "Saddle Eock" or '-jST. Y. Count" 
oyster would not recognize his great- 
grandfather — the Oslrei marthii — if he 
were to meet him in tlie road! 
Eestore, in imagination, the little IG- 
hoofed fossil horse — not larger than a 
jack rabbit — and place him beside a mod- 
ern Clydesdale, Norman or thorough- 
bred. 
Coiitr 1st tlie giant saurian whose re- 
mains were found near Canon City, Colo- 
rado and no w in the Smithsonian jMuseum 
at Washington, with the pigmy lizard by 
the roadside to-day! 1 he one 70 feet 
the other 2 inches in length! 
In the way of vegetable fo-sils, tak(^ 
one of tlio" giant sigillarta of southern 
Kansas, that stood 100 feet tall and 6 ft. 
in diameter, ar.d stand it, in imagination, 
by the side of a "•maiden hair," poly podi- 
um or other fern of to-day! 
A tliorough investigation into the 
causes tliat produced these wonderful 
changes in organic forms will lead to an 
understanding of the true relations of 
fossil fiora and fauna to the types of to- 
day. Thus will a complete view of his- 
torical botany and zoology be had. Such 
an investigation Avill settle all, or at 
least the main points involved in the 
great question of evolution. A study of 
the specimens alibrded b}^ the fossil 
world will determine whether progress- 
ion or retrograssion has been the rule 
with organized luatter. Some of the ex- 
amples given above indicate tlie one and 
some the other. Which accord with the 
rule? Which are exceptions? Are 
there limits beyond which types will not 
develop? It seems to very fully settled 
that one species may be evolved from an- 
other, but may one genus or order evolve 
from another? Arc the lines that divide 
