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



5. Professor TyndalVs Extracts from Rcndu examined. The 

 First Extract. 



I have already adverted to some of Professor TyndalTs slighter 

 and more general claims on behalf of Rendu. But it is at ] 

 303 of Professor Tyndall's work that the more serious allegation 

 is made, that while certain passages from Rendu are well 

 known, from the frequent and flattering references in my work, 

 'others of much greater importance, which have hitherto 

 remained unknown in this country/ which, having 'discovered/ 

 he proceeds to divulge. 



The passages to which attention is thus so significantly 

 directed are only two in number, both relating to the comparison 

 of a glacier with a river. I will consider them separately. 



Quotation A (Glaciers of the Alps, p. 303). It will be desir- 

 able, I believe, to copy the original passage from hVndu, restored 

 to the original French, which has been quoted and translated 

 oy Professor Tyndall : 



'J'ai cherche* k appre*cier la quantite de son mouvempnt; mais je n'ai 

 pu recueillir que des donnees un peu vagues. J'ai interroge mes guides 

 sur la position d'un e"norme rocher qui est au bord du glacier, mais encore 

 sur la glace et par consequent soumis & son mouvement. Les guides 

 m'ont montre* 1'endroit ou il etait I'anuee precedente, et celui ou il t'-fait 

 il y a trois, quatre et cinq ans ; bien plus, ils m'ont moritre 1'endroit cu. 

 il se trouvera dans un an, deux ans, etc., tant ils croient etre certains de 

 la regularity de ce mouvemcut. Cependant leurs rapports n'etaieut pas 

 toujours precisdment d'accord, et leurs indications de temps et de dis- 

 tances manquent toujours de cette precision de mesure et de quantite sans 

 laquclle on est oblig6 de marcher a tatons dans les sciences physiques, 

 mluisant ces diflererites indications a une moyenne, je trouvai que 1'avance- 

 ment total devait etre d'environ 40 pieds par annee. Dans nion dernier 

 voyage j'ai obtenu des renseignements plus certains que j'ai consigned cl 

 chapitre precedent, et 1'^norme difference quise trouve entre les deux resultats 

 provient de se que les demieres observations out et6 faites au milieu du glacier 

 d'ecoulement, qui marche avec plus de rapidite, tandis que les premieres out etc 

 faites sur le bord, ou la glace est retenue par le frottement des parrois [*iVJ 

 rocheuses.' RENDU, pp. 94, 95. 



From the emphasis laid on the last sentence by the italics 

 and capitals of Professor Tyndall in citing this passage, it would 

 appear that what he most insists on as novel, and hitherto over- 

 looked, is the more rapid motion of the central ice, and the 

 retention of the lateral ice by friction ; and in evidence of the 

 'grave misapprehension' to which he alleges that Eendn's 

 statements have been exposed, he cites 1 from my T/ 

 p. 128, the reference which I have made to Rendu's 'estimates 

 of the motion of the Mer de Glace, which has been already 

 1 Glaciert of the Alps, p. 304. 



