CLOUDS ASD RIVERS, ICE AND GLACIERS. 161 



§ 60. Viscous Theory. 



404. Here indeed the merits of the distinguished 

 Racialist last named rise conspicuously to view. From 

 the able and earnest advocacy of Professor Forbes, the 

 public knowledge of this doctrine of glacial plasticity is 

 almost wholly derived. He gave the doctrine a more 

 distinctive form ; he first applied the term viscous to 

 glacier ice, and sought to found upon precise measure- 

 ments a ' Viscous Theory 5 of glacier motion. 



405. I am here obliged to state facts in their historic 

 sequence. Professor Forbes when he began his investi- 

 gations was acquainted with the labours of Rendu. In 

 his earliest work upon the Alps he refers to those 

 labours in terms of flattering recognition. But though 

 as a matter of fact Rendu's ideas were there to prompt 

 him, it would be too much to say that he needed their 

 inspiration. Had Rendu not preceded him, he might 

 none the less have grasped the idea of viscosity, execut- 

 ing his measurements and applying his knowledge to 

 maintain it. Be that as it may, the appearance of Pro- 

 fessor Forbes on the Unteraar glacier in 1841, and on 

 the Mer de Glace in 1842, and his labours then and 

 subsequently, have given him a name not to be for- 

 gotten in the scientific history of glaciers. 



406. The theory advocated by Professor Forbes was 

 enunciated by himself in these words : — c A glacier is an 

 imperfect fluid, or viscous body, which is urged dowt) 



