210 FIFTEENTH LETTER ON GLACIERS. [1848. 



XVIII. FIFTEENTH LETTER ON GLACIERS. 

 Addressed to the Rev. DR. WHEWELL.* 



OBSERVATIONS ON THE ANALOGIES DERIVED FROM MUD- SLIDES ON A 

 LARGE SCALE, AND FROM SOME PROCESSES IN THE ARTS IN FAVOUR 



OF THE VISCOUS THEORY OF GLACIERS. 



Land slips as observed by M. Collin Mr. Milward on the Phenomena of a large 

 Mud-Slide at Malta, and on the Cause of the Dirt-Bands and Wrinkles of 

 Glaciers Connection with Frontal Dip Surfaces of Detrusion in Iron Turn- 

 ings, attended with Vertical Accumulation of Material. 



My dear Sir It is considerably more than a year since 

 you did me the favour to communicate to me the interesting 

 drawing and remarks by your friend Mr. Milward, on a mud- 

 slide on a large scale, which had come under his observation 

 at Malta, and which led him to notice some interesting ana- 

 logies with the structure of glaciers. Again, last August, you 

 communicated some farther reflections and observations by 

 Mr. Milward, and you invited me to send any remarks on 

 the same subject which occurred to me, to be communicated, 

 along with Mr. Milward's papers, to the meeting of the Bri- 

 tish Association. I sent you, on the llth of August, a let- 

 ter, the chief parts of which I shall embody in this one, but 

 which was not read at Swansea, in consequence of the pres- 

 sure of business in the Geological Section, which barely ad- 

 mitted (as I afterwards heard) of Mr. Milward's papers being 

 read, and consequently no discussion took place. Since that 

 time, Mr. Milward, before returning to Malta, was kind 

 enough to place his papers at my disposal, which I then of- 

 fered to Professor Jameson for publication in his Journal, which 

 he accepted, and now allows me to add my remarks on the 

 same subject, which I address to you, as having been the intro- 

 ducer of Mr. Milward's facts, and as having first desired my 

 opinion with regard to them. 



The phenomena presented by mud-slides on a large scale, 

 are not now studied quite for the first time. About two 



* Edinburgh New Philosophical Journal for January 1849. 



