BRITISH ASSOCIATION. 



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masses into Firn, Mer de Glace, &c, believing such divisions 

 did not exist in nature, and were inapplicable to the glaciers 

 of the Polar regions. From an examination of the accounts 

 given by Saussure, Auldjo, Desor, and others^ Dr. Stark 

 was of opinion that there existed no constant differences in 

 the crystaUine structure of the ice in different parts of gla- 

 ciers ; perfect glacier ice, both as to purity and compactness, 

 occurred at all heights ; from which he inferred, that after 

 the crystalline particles of snow became once consolidated into 

 compact ice, no farther change, or enlargement of those 

 particles, occurred till the mass was finally dissolved. The 

 ice of glaciers had always been described as arranged in re- 

 gular layers, but their position and mode of formation, as 

 explained even by the latest writers, was stated by Dr. Stark 

 to be so obscure, that having carefully examined the facts, 

 he had formed conclusions, of which, as they differed from 

 those usually entertained, he proceeded to give a summary, 

 classifying the differences observable in the structure of 

 glacial masses under the following divisions : 



1. Horizontal strata. The author remarked that this was 

 usually termed banded structure, and seemed to be confined 

 to the upper regions of the mountains. The planes inva- 

 riably coincided with the surface of the glacier, the layers 

 being usually I to 3 feet in thickness. They were mentioned 

 by almost all writers on glaciers, and represented in the 

 plates of M. Agassiz's work. Most writers considered them 

 as marking the annual additions to the glacier ; but as the 

 amount of snow falling on the average during the six winter 

 months would produce a much greater thickness of ice than 

 the horizontal layers indicated. Dr. Stark considered that 

 each band denoted a separate fall of snow unless it should 

 appear that snow and ice wasted with nearly as much rapi- 

 dity in the upper as in the lower regions. 



2. Longitudinal and vertical strata. Dr. Stark stated that 



