82 
Proceedings of the Royal Society. 
gregarious in their habits. Four opinions had been proposed as to 
the process by which the mollusks excavate the holes, and are dis- 
cussed by Forbes and Hanley 1. By rasping the rock with the 
sharp edge of the shell ; 2. By dissolving the rock with an acid se- 
creted by the animal ; 3. By grinding with silicious particles attached 
to some part of its body ; 4. By vibratory cilia set in motion by 
the animal, and producing currents of water. But objections have 
been made to all these opinions. 
3. Notice respecting some Artificial Sections illustrating the 
Geology of Chamouni. By John Buskin, Esq. Commu- 
nicated in a letter to Professor Forbes. 
In the Proceedings of the Boyal Society, vol. iii., p. 348, an ac- 
count has been given by Professor Forbes of the discussions which 
had then taken place as to the geological constitution of the chain 
of Mont Blanc, and as to the reality of the alleged superposition of 
the primary rock (gneiss) to the secondary (limestone), near Cha- 
mouni, and at Courmayeur. 
In order to clear up any remaining doubt, Mr Buskin caused sec- 
tions to be made, laying bare the junction at several points of the 
Valley of Chamouni. The results, which are perfectly accordant 
with the conclusions of the above-cited paper, have been kindly com- 
municated by Mr Buskin to Professor Forbes, and are described 
and sketched by him in the following note. The order of the sec- 
tions is from the head of the Valley of Chamouni towards its lower 
or south-western extremity. 
Specimens of the more important rQcks have been placed in the 
Museum of the Boyal Society : — 
44 1. At Crozzet de Lavanchi, on road to Argentiere, under the 
Aiguille de Bochard. 
