125 



March 21, 1849. 

 Dr. A. A. Gould in the Chair. 



Present, sixteen members. 



Mr. Desor, not having been present at the last meeting, 

 introduced the subject then treated of by Prof. Rogers, 

 namely, the ribbon structure of the ice in Glaciers. 



This had not, he thought, been satisfactorily explained before. 

 This was partly owing to a confusion in the minds of those who 

 had discussed the question, between the transverse looped struc- 

 ture and the ribbon structure in question, which is longitudinal. 

 The cause of the former of these was, he thought, pretty well 

 understood. He agreed with Prof. Rogers as to the resemblance 

 in the ribbon ice to narrow bands of slate. At the head of the 

 Glacier, as had been pointed out by Charpentier and Agassiz, 

 after successive freezings and thawings, this ribbon ice is formed, 

 but the plates are not of such regularity and length as lower 

 down. At a lower point their appearance is as Prof. Rogers 

 described them. Sometimes for a mile in length they are per- 

 fectly straight and of uniform thickness. In some places fissures 

 of a few inches depth are seen in this ice parallel to its course, 

 suggesting the question, whether they indicate the cause of the 

 phenomena, or are only the effects of melting. An objection to 

 the supposition that these layers of ice are produced by water 

 freezing in cracks of the glacier exists in the fact, that they 

 extend across deep ravines, and preserve for so great a distance 

 such a strict parallelism and regularity. On the whole, Mr. 

 Desor said he was inclined towards Prof. Rogers's theory, that the 

 ribbon structure is due to a true molecular change in the sub- 

 stance of the ice itself, although it is not as yet demonstrable. 



Prof Rogers said he was glad to hear from Mr. Desor such a 

 confirmation of his own views. He was not before aware that 

 the blue bands are more irregular and infrequent at the upper 

 than at the lower part of the glacier. He regarded the fact as a 



