526 THE LIFE OF JAMES D. FORBES. [APPEND. 



criticism when my Trawls in the Alps are concerned, he lias 

 thought it worth while to signalize three times, in as many 

 different publications, the venial error of the True North being 

 set off on the compass-card of my Map of the Mer de Glace on 

 the wrong side of the Magnetic Nortli, according to which (as it- 

 is stated in the text) the map had been laid down. 1 Yet he 

 allows that the error was corrected by myself nearly ten years 

 before he had any chance of detecting it. 



3. My first References to Rendu's 'Thtforie.' 



The Theorie des Glaciers de la Savoie of Bishop Rendu ap- 

 peared in the 10th volume of the Memoirs of the Academy of 

 Chambe'ry in 1841. 2 It comprises 120 rather widely printed 

 octavo pages. I heard it spoken of in August 1841 by M. Agassiz 

 or by his friends, on the Glacier of the Aar, certainly not in very 

 respectful terms. It appeared to be regarded by them as the 

 work of a visionary. After leaving the glaciers in the same 

 year, I saw the Theorie in the hands of a Swiss friend, but so 

 cursorily, that the circumstance would probably have escaped 

 me, but for a reference to it in a note to an article in the Edin- 

 burgh Review for April 1842, which was written by me, from 

 which it also appears that the Essay itself seemed to me to be 

 by no means worthy of the ridicule which I had heard applied to 

 it. There can be no reasonable doubt that my main if not sole 

 interest in inspecting M. Kendu's book on this occasion, was 

 to endeavour to find a reference to the ' veined structure ' of 

 glaciers, which was then the engrossing subject of discussion. 

 I did not find any account of it there. 3 



That a glacier moves like a sluggish river, and under the same 

 laws, was an idea which first clearly entered my mind as a 



of the Aar, which he considered as demonstrative of its correctness. The 

 former theory that the glacier merely slides by gravity over its inclined bed 

 was still later defended by the aid of assumptions of a very arbitrary kind. 

 At this stage of the subject only a stinted measure of approbation was by many 

 persons awarded to the observations contained in my work, the general fad 

 that glacier ice behaves like a plastic mass being then resisted, though neces- 

 sarily involved in the special facts which could not be denied. These occur- 

 rences, well known to those who interested themselves in the subject fifteen 

 years ago, might easily escape the notice of the reader of the present day. 



1 The magnetic variation is also correctly stated in the text (p. 123, 1st edit.) 

 at 19 W. 



8 Since writing the above passage, I find in the preface to Dr. Charpentier's 

 Essai sur les Glaciers (Lausanne, 1841), that he received a copy of Renclu's 

 Theorie on the 24th October, 1840, and that it bore the date of 1840. This 

 must have been on the separate copies. 



8 Compare Travels in the Alps, p. 29, and also extract (a), page 11 of the 

 present Reply [p. 528]. 



