162 THE FOKMS OF WATER IN 



dopes of certain inclination by the natural pressure 

 of its parts. 5 In 1773 Bordier wrote thus: — ' As the 

 glaciers always advance upon the plain, and never dis- 

 appear, it is absolutely essential that new ice shall per- 

 petually take the place of that which is melted : it 

 must therefore be pressed forward from above. One 

 can hardly refuse then to accept the astonishing 1 truth, 

 that this vast extent of hard and solid ice moves as 

 a single piece downwards. 5 In the passage already 

 quoted he speaks of the ice being pressed as a fluid 

 from above. These constitute, I believe, Bordier's con- 

 tributions to this subject. The quotations show his 

 sagacity at an early date ; but, in point of completeness, 

 his views are not to be compared with those of Rendu 

 and Forbes. 



407. I must not omit to state here that though the 

 idea of viscosity has not been espoused by M. Agassiz, 

 his measurements, and maps of measurements, on the 

 Unteraar glacier have been recently cited as the most 

 clear and conclusive illustrations of a quality which, at 

 all events, closely resembles vicosity. 



408. But why, with proofs before him more copious 

 and characteristic than those of any other observer, does 

 M. Agassiz hesitate to accept the idea of viscosity as 

 applied to ice? Doubtless because he believes the 

 notion to be contradicted by our every-day experience 

 of the substance. 



409. Take a mass of ice ten or even fifteen cubic feet 



