368 MODE OF PLOW OP A VISCOUS P1UID. [Aug. 1895, 



only show that the lower layers of the ice are densely charged with 

 detritus, but explain the manner in which it is introduced from the 

 bottom. 



Again returning to the experiment, it will be observed that the 

 elevation of the third layer as it surmounts the barrier is so great 

 that it is carried completely clear of it ; and if such a disposition of 

 ice and barrier should occur in nature, it would be possible to find 

 boulders, on the far side of a mountain, which had been brought 

 from hills lower than itself, situated on its near side ; while on 

 the barrier and in the intervening regions such boulders might 

 prove, to the embarrassment of the observer, to be wholly absent. 

 Whether such an extreme case has been recorded I do not know, 

 but instances of boulders which have been carried right over 

 mountain-summits are not infrequent. 



A much controverted question has been the mode of flow of 

 glaciers over deep lake-basins, and the suggestion has been made 

 that the sheet of ice above the general level of the brim of a lake- 

 basin would shear away from that below, which would remain 

 quietly at rest like a stagnant pool. Such a conception is distinctly 

 inconsistent with the results of this experiment, which show that 

 the ice would certainly be in motion throughout its mass. How 

 far the ice might actually be capable of eroding a lake-basin is a 

 question which experiments in progress may assist in solving. 



Discussion. 



Mr. "W. "W. "Watts, referring to two scratched stones exhibited 

 by him, stated that they had been picked up on a moraine which 

 came up through the ice at the lower part of the Findelen Glacier, 

 near Zermatt. Although the stones were clearly found at a lower 

 level than their point of origin, and although it was quite possible 

 that the moraine made its appearance at a lower level than the 

 point at which the stones had touched the bed of the glacier, it was 

 quite clear that they had been at the bottom of the glacier, and had 

 made their way up through the ice in the same way as the grains of 

 sago in Prof. Sollas's experiment. 



Sir Henry Howokth also spoke. 



