344 Scientific Proceedings, Royal Dublin Society. 
to realize the nature of the phenomena, which it is thought may 
in this manner be so simply explained. I believe, however, that 
all who do possess a knowledge of these subjects will agree 
that such an explanation cannot be seriously entertained with 
reference to the splitting off of shells of rock averaging six 
inches in thickness. 
Although I am unable to state positively that such is the case, 
it seems to be highly probable that these domes are really por- 
tions of complete spheroidal masses, which have become isolated 
from their original surroundings by the erosion of softer, more 
readily decomposable, parts of the rock. On the small scale, in 
the case of both volcanic and plutonic rocks (basalts and 
granites), most geologists are familiar with the pseudo-boulders, 
which are the result of local hardness and the removal of softer 
more easily decomposed, portions. Such pseudo-boulders fre- 
quently have a concentric ex-foliating structure, but this is 
generally accompanied by much decomposition of the layers and 
alteration of the mineral components, which is not found to be 
the case with the shells in the domes, as the rock is always firm 
aud sound, yielding a metallic rg on being struck, or even 
when 77 situ it is trodden under foot. Its fracture, moreover, is 
sharp and angular. 
On the whole, it seems probable that the spheroidal jointing 
may have been produced by shrinkage on cooling after erystalliza- 
tion had taken place.* 
As I said above, this theory of origin is imperfect, but I 
venture to think the main object of this paper has been attained, 
namely: It has been demonstrated that dome-shaped hills and 
surfaces, resembling roches moutonnées, may be produced by a 
cause other than the action of glaciers. This fact being admitted, 
I shall now apply it to a locality in Switzerland, where, in the 
midst of glaciers, the same structure occurs, largely developed, 
and where, so far as I have been able to refer to authorities, the 
rounded surfaces are described as being produced by glaciers, 
without any suggestion as to the possibility of the form being 
in part due to other causes. 
When crossing the Grimsel Pass last October, I first met in 
* Another explanation has been suggested by the Rev. Professor Haughton, in 
reference to the Swiss rocks, namely, that these planes may be due to a form of cleavage 
produced under great pressure during upheaval of the mountain ranges. 
