68 NINTH LETTER ON GLACIERS. [1845. 



X. NINTH LETTER on GLACIERS, addressed to 

 PROFESSOR JAMESON. * 



Remarks on the Recent Observations made on the Glacier of the Aar (in 1844) by 

 direction of M. Agassiz. New Confirmation of the Plastic Theory. Conden- 

 sation of the Glacier in its downward course in consequence of Frontal Resis- 

 tance Continuity of Motion Motion accelerated in Fine Weather Excess of 

 Central Velocity of the Glacier Motion of Glaciers of Second Order, and of 

 Snow Beds.* 



EDINBURGH, 7th March 1845. 



My dear Sir However satisfied one may be with the con- 

 clusiveness of their own experiments, it is always pleasing when 

 they are confirmed by others even in their minuter particulars, 

 especially if the observations have been made in circumstances 

 at all different. In this respect, I find with pleasure, from a 

 communication read at the Institute on the 9th December last, 

 that M. Agassiz's coadjutors on the glacier of the Aar have 

 obtained results so perfectly accordant with those which you 

 have done me the favour of publishing on former occasions, that 

 they would have satisfactorily established, had earlier observa- 

 tions been awanting, the viscous theory of glacier motion with 

 which alone they are reconcileable ; the single seeming antago- 

 nism to my own measurements being one which tells still more 

 in favour of that view. 



I propose to give a brief summary of these results, and to 

 show their correspondence with my own. This correspondence 

 amounting almost to coincidence is, of course, to me, a satis- 

 factory guarantee for their accuracy, as far as they go. By 

 others, the goodness of the instruments, and the expertness of 

 the observers, must, in the mean time, be taken for granted. 



It is hardly necessary to premise that M. Agassiz and his 

 friends now admit that all glaciers move fastest at the centre, 

 and slowest at the sides. 



* Edinburgh New Philosophical Journal, April 1845. 



