{ 9341. J 
XLVI.—ON SPHEROIDAL JOINTING IN METAMORPHIC 
ROCKS IN INDIA AND ELSEWHERE, PRODUCING 
A STRUCTURE RESEMBLING GLACIAL “ROCHES 
MOUTONNEES,” sy V. BALL, ma., F.G.8., oF THE GEOLOGICAL 
Survey oF Inpia. Puates 21, 22, and 23. 
[Read December 15th, 1879. ] 
Some years ago, when engaged in the geological examination 
of a portion of Western Bengal, where metamorphic rocks 
exclusively prevail, I frequently met with zones or narrow tracts 
wherein a particular form of rock prevailed, which formed rounded 
boss-like or dome-shaped hills, of a character which I had never 
encountered elsewhere, and of the origin of which I had not then, 
as I have not since, met with any published explanation. Since 
that time I have frequently seen similar and similarly formed 
hills, not only in various other parts of India, but, quite 
recently, I have found the same structure occurring in rocks 
possessing the same lithological characters in Switzerland. It is 
in consequence of this last observation, and because I believe 
the structure has in that country not been duly recognised, that 
I now enumerate the following facts, and venture to account for 
them by a theory which is, however, as yet, confessedly somewhat 
imperfect. 
The dome-shaped masses in India, which I have alluded to, 
rise abruptly from the surrounding soil or rocky surface, as the 
case may be, sometimes singly and sometimes in groups—the 
individual domes being only occasionally in very close juxta- 
position to one another. 
At first sight they appear to be perfectly solid masses of rock, 
with symmetrical rounded or rather ellipsoidal contours. In 
many, if not in most cases the surfaces are so smooth and steep 
that under the influence of tropical rains they are incapable of 
retaining any covering of soil, and consequently, besides a small 
fern which manages to obtain a footing in cracks and fissures, 
vegetation is seldom found upon them. The size of these domes 
varies, but the height rarely exceeds 100 feet, and is generally 
