﻿274 Rev. T. G. Bonney — Formation of Cirques. 



maintained. Of those which I described, some indeed look N. ; but 

 the Creux de Champs and Fer a Cheval have a N.W. aspect, the 

 former perhaps rather W.N.W. ; the Cirque Am Ende der Welt looks 

 S.W., and the two under the Kothstock almost due S. I am, there- 

 fore, disposed to regard the fact which he notices as quite indepen- 

 dent of any general theory of the formation of cirques. 



He further points out that there is a connexion between the posi- 

 tion of cirques and the height of the snow-line ; and that cirques 

 and glaciers are commonly associated. Hence he concludes that the 

 cirques were excavated by the glaciers, and describes the mode in 

 which he conceives this to have been effected. There is, no doubt, 

 some connexion between the level of the snow-line and of the bed of 

 the cirque. In the Alps, however, the bed of the more important 

 cirques is generally far below the former. (Professor Gastaldi's 

 statement I think places the lower limit rather too high.) Most of 

 those which I describe have their floors about 4500' to 6000' above 

 the sea-level ; but I have also seen them much higher. The rela- 

 tion, however, in no way militates against my view, because, when 

 the walls of the cirque rise up beyond the snow-line, the conditions 

 most favourable to stream erosion prevail, as a perennial supply of 

 snow rests on the higher ledges and slopes ; in fact, I think it would 

 be difficult for a large cirque to be formed, unless the streams were 

 supplied by snow-beds. Again, as to the connexion between cirques 

 and glaciers. Mr. Helland says, "Where the mountains are higher 

 and isolated glaciers are very numerous, cirques are also numerous ; 

 and as isolated glaciers are here capable of being formed and main- 

 tained at an inconsiderable height above the sea, the cirques also 

 occur at but slight elevations." As I have just observed, proximity 

 to the snow-line is undoubtedly favourable to the formation of 

 cirques, and I quite agree that the abov^e association is one of cause 

 and effect, only that which Mr. Helland deems cause I consider effect 

 — no doubt a rather important difference. I believe that isolated 

 glaciers abound where cirques abound, because a cirque with its 

 sheltered recesses is peculiai'ly favourable to the formation of a 

 glacier. This connexion seems to me no more to prove his case than 

 the occurrence of a puddle in the sheltered corner of a quarry proves 

 that the water excavated it. 



I proceed then to offer reasons why I consider Mr. Helland's 

 theory of the formation of cirques inadequate. It is thus stated — 

 " As the temperature ai-ound the glaciers constantly varies about the 

 freezing-point, the incessant freezing and thawing of the water in 

 the cracks in the rock may split it, and the glacier may do the work 

 of transportation for the fragment's thus broken loose. On examining 

 the interior of an empty cirque, we observe that a bursting, not a 

 scooping out of the rock has taken place." If I understand him 

 rightly, he regards the cirque as formed by a sort of process of per- 

 petual " tooth drawing," — the bed or slope of the mountain beneath 

 the glacier is cracked by changes of temperature, the fragments are 

 caught by the superjacent ice, lifted up, perhaps wrenched out, and 

 borne away. Now with regard to this theory, I must remark in 



