B.] FORBES, GUYOT, AND AGASSIZ. 547 



by conjoint inspection, that the structure in question was trace- 

 able all across the glacier of the Finster Aar. 



Fact 6. M. Agassiz, unwilling to admit that he could formerly 

 have overlooked so palpable a structure, expressed a frequent 

 doubt whether this structure had not been superinduced since 

 his last visit. 



Fact 7. I took the following means of proving that this 

 could not be the case. I showed him some crevasses, and asked 

 him how old he supposed them to be ? he answered, several years; 

 they certainly had not opened since last summer (3840). I 

 showed that the veined structure crossed these crevasses, and 

 dislocated by them, as in the margin, and, therefore, must 

 have been anterior to their formation. 



l^et 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 state- 

 ment of facts : 



EXTRACT FIRST. Rev. J. M. Heath to Professor Forbes (printed by 

 Mr. 1 1' nth' s permission). 



1 TRINITY COLLEGE, 8th March, 1842. 



' . . . But those who were there this summer have very different evidence 



I hat tliis was a new fact. I remember when it was first remarked, Agassiz 



ie had seen it before, but not to such an extent. That it had a peculiar 



>u to the medial moraines, and would not be found in the centre of the 



r; that it was //V/V//, and owing, as lie believed, to the sand, 



If in parallel straight lines, and produced these incisions by 



melting the ice. The afternoon was taken up in what 1 then thought a very 



SIIJK rlluous endeavour to make out whether it was superficial or not, and I 



he maintained the contrary opinion until the discovery of the great ho! 



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 



nf melting, occasioned by a linear arrangement of sand on the 



ie.e, washed from the moraines, and intercepting here and 



the sun's rays? or, Whether it was occasioned by t he 



unequal action of the weather on alternating vertical bands of 



friable and of compact ice, of which the Racier is composed. 



M. Agassiz appears, upon Mr. Heath's testimony and my own, 



to have taken the former view, whilst I took the latter. Accord- 



. him, tl ..is striated on its surface, because the sand 



i lines; according t<> me, the sand lay in lines, because the 



veined structure t/imnt/faml ?7x mass. 



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

 when I requested him to say whether the al.nve-eite.l facts were 

 lately stated or not. In a letter to me, dah-d -'.'th March, 

 he says: 



N 



