136 Professor Forlcs on the First. Dlscotcry of the 



crevasses, and was dislocated by them, as in the mai'gin, and, 

 therefore, must have been anterior to their formation. 



Let us hear the evidence of Mr Heath and M. Agassiz, the 

 only witnesses present besides the guide. 



Mr Heath wrote to me thus, on sending him the above 

 statement of facts : — ■ 



Extract First. — Ilco. J. M. Heath to Professor Foi'hes, (printed 

 hif Mr Heath's j^crmkdon.) 



Trinity College, Hlh Marcli 1012. 



" * * But those who were there this summer have very different 

 evidence that this was a new fact, I remember when it was first re- 

 marked, Agassiz said he had seen it before, but not to sucli an extent. 

 That it had a peculiar relation to the medial moraines, and would not 

 be found in tlic centre of the glacier ; that it was only superficial, and 

 owing, as he believed, to the sand which placed itself in parallel straight 

 lines, and produced these incisions by melting the ice. The afternoon 

 Avas taken up in what I tlien thought a very superfluous endeavour to make 

 out whether it was superficial or not, and I believe he maintained the 

 contrary opinion until the discovery of the great hole of which you have 

 given a drawing," 



It will be observed, then, that the whole question lies in 

 this, Whether the lined appearance of the ice was due to an 

 inequality of melting, occasioned by a linear arrangement of 

 sand on the surface, washed from the moraines, and inter- 

 cepting here and there the sun's rays I — or, ^Vhether it was 

 occasioned by the unequal action of tlie weather on alternat- 

 ing vertical bands of friable and of compact ice, of which the 

 glacier is composed. M. Agassiz appears, upon Mr Heath's 

 testimony and my own, to have taken the former view, whilst 

 I took the latter. According to him, the ice was striated on 

 its surface, because the sand lay in lines ; according to me, the 

 sand lay in lines, because the ice has a veined structure tltroucjh- 

 oiit its mass. 



M. Agassiz, the other witness, admitted as much himself, 

 when I requested him to say whether the above-cited facts 

 Avere accurately stated or not. In a letter to me, dated 20th 

 March 1842, he says, — 



