On a Sooty Deposit on the Surface of the Sea. 3 



self with equal care to that as to other parts of my writings, 

 he would have observed coincidences in our views which he 

 appears not to have noticed; and he would probably have 

 hesitated before laying down so broadly as he has done, an 

 objection to the Viscous Theory, very easily refuted, and 

 some peculiar views which he considers distinctive of his 

 manner of considering the subject, from De Saussure's and 

 my own. I shall probably, on another occasion, endeavour 

 to shew that, by following out his own principles, the results 

 must inevitably merge in mine, when what is inadmissible 

 shall have been subtracted. — I remain, my dear Sir, yours 

 very truly, 



James D. Forbes. 



P.S. — .The influence of the Dimension, Slope, and absolute 

 Elevation (or surrounding temperature) of glaciers upon their 

 motion, is a matter of observation in detail which oflfers no 

 peculiar difficulty, and which deserves to be extended. Hav- 

 ing measured the rate of motion of perhaps the largest glacier 

 in Switzerland (the Aletsch), I have also measured one of the 

 smallest, a glacier of the second order, near the Hospice of 

 the Simplon, almost 8000 feet above the sea, and not many 

 hundred feet in length. The velocity was little more than 

 an inch in twenty-four hours, a result corresponding with the 

 extreme dryness of the neve at that elevation, indicated by 

 the very trifling issue of water from beneath, and to the in- 

 significant vertical pressure of so small a mass, notwithstand- 

 ing its considerable slope. A similar result, it must be 

 owned, might be expected in this case upon almost any 

 theory. 



Extract from a Letter from JRev. George B. Warren^ to Br 

 Davy^ relative to a Sooty Deposit on the Surface of the Sea^ 

 off the Coast of Devon. 



Your paper in Jameson'*s Edinburgh Philosophical Journal on 

 the carbonaceous deposit on the lakes of Westmoreland, recalls 



