678 GEOLOGY OF OHIO. 
which the village of Yellow Springs derives its name will be treated by 
itself, but all along the gorges in the Niagara limestone voluminous 
springs are issuing, which are making extensive calcareous deposits, 
sometimes in dome-shaped stalagmitic masses under the dripping of the 
springs, but more frequently mingled with the earthy and organic prod- 
ucts over and among which the waters flow in short slopes to the valley. 
The vegetable, and sometimes the animal, matters that the water meets 
with are often incrusted by the travertine, and are then said in popular 
language to be petrified. A specimen submitted to analyses gave the 
following result (Wormley): 
Carbonate Of dime ee ey OS UU EN LU a RU EY Rena 95.70 
Carbonate! of magnesia ses. boi lee- secs casetacaclen eae eee eee ne 3.73 
AlUMING AN GMTOM eer re es ac hee aces a eee ee ee eat anne 0.50 
99.93 
Another specimen examined shows the following composition (Mees): 
Carbonate of lime ....7....0...:... CE OCS SCE EOD IGE EOIC ace Ooiocd paGoda deKoSEtioe decuecdobods 97.60 
Carbonate: Of MAGNESIA. sii scbe lest seaviccs coe eeleeee sete ee eee eee ei 
SHICTOUSMALER LIE Fe Soaeces a sabe ocace scceeause soem ene ee eee cae eee a Son eee Oa il 0.60 
99.41 
In this connection the very interesting fact is to be noted, that while 
the rocks from which the springs issue are dolomitic, containing nearly as 
much carbonate of magnesia as carbonate of lime, the travertine is almost 
purely calcareous. It therefore appears that in magnesian limestones 
permeated by atmospheric waters the proportions of magnesia must be 
constantly, though of course very slowly, increasing. The varying pro- 
portions of carbonate of magnesia in the limestones of the Cedarville 
division may be, in part, accounted for in this way. By reference to the 
table of analyses on page 675, it will be seen that this substance in one 
instance makes fifty per cent. of the entire weight of the rock. A greater 
exposure than ordinary to carbonated waters would serve to explain this 
increased proportion. It may be added that the location of the quarry 
from which the stone yielding this result was obtained, in the flat-lying 
tract of Darke county, would seem to indicate the long-continued pres- 
ence of such carbonated water. 
Further: as far as the explanation above given applies, it ought to be 
found that the more highly magnesian the limestone the less should be 
its specific gravity. A few facts under this head are here given. The 
determinations of specific gravity were furnished by Prof. Mendenhall, of 
the Ohio Agricultural and Mechanical College. The comparison is not 
