140 Reports and Proceedings— 
and the rapid decomposition of the whole series. When the change 
of thickness of the coal beds and the large number of thin coals— 
usually overlooked—are given due consideration, strong doubt is 
thrown upon the identifications that have been often attempted, 
between the coal in one mine and that in another mine a mile 
or more away. The probabilities are that the coal of economic 
importance in the one mine is represented by some one of the 
smaller neglected coals in the other. 
The areas of crushing and faulting are, owing to the softness of 
the rocks, more impervious to water than the undisturbed portions 
of the beds. In this I differ from Mr. Clifford, when he says, ‘‘ The 
measures which overlie the coke seams are very much fissured, and 
consequently the pits working coke are more heavily watered than 
coal pits. Some of the most promising ones in the northern end of 
the field had to be abandoned on that account.” ! This idea probably 
arose from the fact that the workings in the northern portion of the 
coal area carried on by many owners, at various times, without 
system, have intersected each other, so that water from one coke pit 
will now flow to any other. Thus, the perviousness to water, which 
has caused the abandonment of these mines, is due to artificial and 
preventable rather than natural or wide-spread causes. 
F. H. Newer... 
ISAT HOpSssesS) veINViD) J aeyO) Gps aD saline. 
a hss 
GroLocicaL Society or Lonpon. 
I.—January, 23, 1889.—W. T. Blanford, LL.D., .F.R.S., Vice- 
President, in the Chair.—The following communications were read : 
1. “On the prevailing Misconceptions regarding the Evidence 
which we ought to expect of former Glacial Periods.” By Dr. James 
Croll, F.R. S. Communicated by T. G. Bonney, D.Sc., F.R.S., F.G.S. 
The imperfection of the geological record is greater ‘than i is ‘usually 
believed. Not only are the records of ancient glacial conditions 
imperfect, but this follows from the priciples of geology. The 
evidence of glaciation is to be found chiefly on land-surfaces, and 
the ancient land-surfaces have not, as a rule, been preserved. 
Practically the several formations consist of old sea-bottoms, 
formed out of material derived from the degradation of old land- 
surfaces. The exceptions are trifling, such as the under-layers 
of coal-seams, and dirt-beds like those at Portland. The trans- 
formation of an old land-surface into a sea-bottom will probably 
obliterate every trace of glaciation; even the stones would be 
deprived of their ice-markings; the preservation of Boulder-clay, as 
such, would be exceptional. The absence of large erratic blocks in 
the stratified beds may indicate a period of extreme glaciation, or 
one absolutely free from ice. The more complete the glaciation the 
less probability of the ice-sheet containing any blocks, since the 
rock would be covered up. Because there are no large boulders in 
1 Clifford’s paper, p. 1s. 
