arriving at a correct theory of its accumulation. Since 
then a paper has been read at the Geological Society, by 
Mr. Trimmer, in which he attempts to explain them by 
supposing that masses of ice had been fixed amongst the 
beds when they were deposited, and that, on these sub- 
sequently thawing, the strata above sunk down into the space 
they occupied. Both these suppositions are undoubtedly 
true causes, and in some parts of the globe contorted strati- 
fication must now be produced by the action of both. My 
own opinion is that some of the contortions in the drift are 
due to one, and some to the other, and that neither alone is 
sufficient to account for all that occur. 
Those to which I shall particularly call attention are in 
the neighbourhood of Bridlington ; for the drift there, con- 
sisting to a great extent of horizontally stratified thin-bedded 
sand and clay, exhibits many facts which cannot be observed 
when, as is frequently the case, the boulder clay constitutes 
nearly the whole. 
In the first place I will describe an example of what 
appears to me to require the explanation suggested by Mr. 
Trimmer. This is shown in Fig, 1, Plate V., in which, as well 
as in all the others, those parts with round marks are boulder 
clay ; those with dots, gravel ; and the rest more or less 
fine sand: the line drawn below each being the scale of 
one yard. At the lower part is boulder clay, in which there 
appears to have been a kind of inverted funnel-shaped cavity, 
much broader at the bottom than at the top. This is now 
filled with gravel and sand, which is arranged in such a 
manner as to indicate that it entered through the opening 
at the top in a mass, and not as if deposited in it gradually. 
The beds just above are broken up, as though they had in 
part subsided into the supposed vacuity, but a little higher 
up they are horizontal and undisturbed. Such a case as 
this, I think, could be readily explained, by supposing that a 
mass of ice was lodged amongst the boulder clay, oyer 
