1877. ] 251 {Prime. 
a portion of its water, has excavated a cave a short distance into it. At 
the west end of the hill, near the small opening where that portion of the 
creek forming the spring disappears, there occurs a new species of Mono- 
craterion, as yet undescribed. Of this half a 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 north-east of this five or six specimens of a lingula 
were found in John Schadt’s quarry, but it is impossible to determine its 
species. About half a mile west of Helfrich’s Spring a single specimen 
of an orthoceratite was found close to the Jordan, just north of Scherer’s 
Tavern, but so imperfect that its species is undeterminable. Finally a 
specimen of Euomphalus was found on Nero Peters’ farm, two miles east 
of Ballietsville. 
Not a single fossil has been thus far found in the No. II limestone 
of Northampton county. 
The No. II limestone, like the Magnesian limestone of the Mississippi 
Valley, isexceedingly soluble. Streams constantly disappear in the ground, 
forsaking their original beds except when the volume of water is too great 
to be carried off by the subterranean channels, and reappearing again as 
springs at greater or less distances. The effects due to this solution of the 
limestone are very great. Not only are small sink-holes very common, 
but beds are found often much contorted locally in a manner which can 
only be explained by supposing them to have dropped down by their own 
weight into caverns excavated by the water beneath them. Possibly also 
the contortion of the hydromica beds as developed in the brown hematite 
mines at the junction of the limestone with the No. III slates is due to the 
same action, rendered more prominent by the passage of streams from the 
slate to the limestone, where the solving action could begin. The differ- 
ent 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 
mechanical or physical than chemical. Knowing as we do so little as to 
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 which to base such theories. No 
better illustration of the darkness amidst which geologists are seeking light 
can be given than by stating that we are in complete ignorance of the 
causes which produce different layers of limestone, almost identical in com- 
position, the one above the other. We can explain alternations of shale, 
sandstone, and limestone by changes in depth of the sea in which they 
were formed ; but such an explanation does not hold good where the same 
rock continued to be formed. Why should the sediment, whether chem- 
ical or mechanical, have formed a continuous layer an inch to several 
