346 Scientific Proceedings, Royal Dublin Society. 
stries au dessus de la Handeck,” figured by Agassiz in his classic 
work on glaciers, may owe their form in part to this structure, 
which seems to be almost a proper characteristic of this form of 
granitic gneiss wherever it occurs. But in making this last 
suggestion, I do so with some hesitation, as I am not sure of the 
exact locality of the particular domes referred to. 
Baedeker,* too, speaks of the granite rocks in this area being 
rounded and polished by glacier friction. 
It would probably be easy to multiply such references, but I 
have not yet succeeded in finding any allusion to the concentric 
shell structure of the gneiss itself as being, to say the least, an 
important factor in the production of the surfaces which have 
attracted so much notice on the northern slopes of the Grimsel. 
* Guide to Switzerland. 
EXPLANATION OF PLATES. 
Puate 21.—Boss of Porphyritic Gneiss with outer shell partly broken 
up and fallen. North of Parulia in the District of 
Manbhum, Bengal. 
22,—Portion of Boss with accompanying “ tor” of Porphyritic 
Gneiss. District of Manbhum, Bengal. 
23.—Conical-shaped Boss of Porphyritic Gneiss. Near Jhulda, 
District of Manbhum, Bengal. 
) 
NotE ADDED IN THE Press. I am indebted to Professor O'Reilly for calling my 
attention to Professor Whitney’s Geology of California, where in the description of 
the Sierra Nevada, domes of precisely similar character to those in India are alluded to, 
and regarding which Professor Whitney remarks, “That this structure is not the result of 
the original stratification of the rock is evident from a study of the phenomena, which do 
not indicate anything like anticlinal or synclinal axes, or any irregular folding. The 
curves are arranged strictly with reference to the surface of the masses of rock, showing 
clearly that they must have been produced by the contraction of the material while cooling 
or solidifying.” His explanation of the structure, therefore, is identical with mine—near 
the San Joaquin a remarkable dome which rises to the height of 1,800 feet “ presents 
exactly the appearance of the upper part of a sphere, or as Professor Brewer says, of the 
top of a gigantic balloon struggling to get up through the rock.” The same description, 
except as regards the height, might be applied to many of the domes which I have seen 
in India. 
