M. Renoir on the Glaciers of the Vosges- 293 



changed their level, and done so without entirely altering their 

 place ? Was the epoch when ice could continue permanent at 

 about 400 metres of absolute height, between St Maurice in 

 the Valais and Bex, the lowest point at which I could observe 

 its traces among the Alps, the same as that when glaciers de- 

 scended to the same level among the Vosges at Wesserling 

 and Giromagny ? 



Now, we know that, oftener than once, upwards of fifty 

 spots have been counted on the sun's disc, many of which have 

 been calculated to occupy a surface quadruple the extent of 

 that of our globe, and continued for many years. It is on re- 

 cord that about the year 535 the light of the sun was diminished 

 during fourteen months, and that in 625 the half of the disk 

 was obscured for a whole summer. There is no reason to 

 regard this last spot as a maximum ; could the sun, by en- 

 veloping himself entirely in a sombre veil, at one time, have 

 plunged us and our planets into thick darkness and universal ice \ 



Finally, in the planetary spaces, the temperature being un- 

 equal, like the dispersion of matter, could our sun, in its move- 

 ment, now known, round a centre with which we are yet un- 

 acquainted, have drawn all his system along with him into a 

 colder medium, from which he issued only to be plunged into 

 it again, at determinate epochs, which we may perhaps one 

 day be able to calculate ? 



It is not in a simple note like the present that we can at- 

 tempt to discuss such questions as these ; besides, M. de Char- 

 pentier will soon supply us with reasons which will satisfy all 

 our requirements on the cause, probably accidental, of the for- 

 mation of large glaciers. 



Since M. Agassiz has discovered polished surfaces on the 

 southern declivities of the chain of Jura, which the Society 

 verified at its meeting at Porrentruy, we may believe with 

 him and M. de Charpentier, that glaciers formerly covered all 

 the great Swiss valley ; but considering that I cannot find 

 traces of the ancient existence of glaciers in plains remote 

 from mountains, I am led to believe that, at least in our 

 southern parts of Europe, glaciers have never extended much 

 beyond the foot of these chains ; that they may have con^ti" 



