Proceedings of the British Association. 59 



Square, Glasgow. On the 20th of January, 1834, a terrible 

 earthquake occurred in New Grenada, by which the large towns 

 of Popayan and Pasto, were entirely demolished, and many thou- 

 sands perished. On the 21st of September, iS34, Mr. Hamilton 

 experienced a most severe shock, in which the movements of the 

 earth were entirely vertical, and seemed to take place twice eve- 

 ry second. He mentions also, the terrible earthquake on the 

 coast of Chili, February 5, 1835, by which the seaport of Con- 

 ception and Talcahuano, the capital of the province, were totally 

 destroyed. The sea then retired several times to a great distance, 

 and returned in immense billows. It is believed that new banks 

 were then thrown up from its bottom, and that it was on one of 

 these, that the Challenger, ship of war, was wrecked a few 

 months after. 



M. Agassiz made a communication on the subject of glaciers 

 and boulders in Switzerland. He particularly drew attention to 

 facts relative to the mode of the movements of the glaciers, which 

 he attributes to the continual introduction of water into all their 

 minutest fissures, which, in freezing, constantly expands the mass. 

 The effects of the movement produced by this expansion, upon 

 the rocks beneath the ice, are very remarkable. The bases of the 

 glaciers, and the sides of the valleys which contain them, are al- 

 ways polished and scratched. The fragments of the rocks that 

 fall upon the glaciers are accumulated in longitudinal ridges on 

 the sides of the ice, by the effects of the unequal movement of its 

 middle and lateral masses. The result is longitudinal deposits of 

 stony detritus, which are called morains ; and as the glaciers are 

 continuall}'' pressed forwards, and often in hot summers melted 

 back at their lower extremity, it results that the polished surfaces, 

 occasioned by friction on the bottom and sides, are left uncovered, 

 and that the morains, or curvilinear ridges of gravel, remain upon 

 the rocks formerly covered by the ice, so that we can discover by 

 the polished surfaces and the morains, the extent to which the 

 glaciers have heretofore existed, much beyond the limits they now 

 occupy in the Alpine valleys. It even appears to result from the 

 facts mentioned by Prof. A., that enormous masses of ice have, at 

 a former period, covered the great valley of Switzerland, together 

 with the whole chain of the Jura, the sides of which, facing the 

 Alps, are also pohshed, and interspersed with angular erratic rocks, 

 resembling the boulders in the morains ; but so far different, that 



