F. Prime, Jr.—Lower Silurian Fossiis, 265 
dozen casts have been found; but all efforts to discover the 
fossil itself have been hitherto unsuccessful. This discovery is 
the more interesting as the genus Monocraterion has hitherto 
only been known to occur in Sweden. 
About half a mile northeast of this five or six specimens of 
a Lingula were found in John Schadt’s quarry, but it is impos- 
sible to determine its species. About half a mile west o l 
frich’s Spring a single specimen of an Orthoceratite was found 
_ close to the Jordan, just north of Scherer’s Tavern, but so im- 
perfect that its species is undeterminable. Finally a specimen 
of Huomphalus was found on Nero Peters’ farm, two miles east 
of Ballietsville. 
Not a single fossil has thus far been found in the No. IL 
limestone of Northampton county. 
The No. II limestone, like the Magnesian limestone of the 
Mississippi Valley, is exceedingly soluble. Streams constantly 
isappear in the ground, forsaking their original beds except 
when the volume of water is too great to be carried off by the 
subterranean channels, only to reappear again as springs at 
eater or less distances. The effects due to this solution of the, 
action could begin. The different beds too are soluble in very 
different degrees; some apparently yield at once to the eroding 
action of water, while others afford a resistance to this operation 
for reasons as yet unknown, but which are probably rather me- 
chanical or physical than chemical. Knowing as we 
little of the conditions, under which the different layers of 
limestone, almost or quite identical in composition, were 
formed, we can only speculate that those layers which resisted 
erosion were more compact, hard, and dense, perhaps more 
metamorphosed by a subsequent crystallization than the others, 
while we actually have no facts on W ich to base such theories. 
No better illustration of the darkness amidst which geologists 
other. We can explain alternations of shale, 
limestone by changes in depth of the sea in which they were 
formed ; but such an explanation does 
