268 Mr. J. Y. Buchanan- [May 8, 



us is^ the solidification rather than the crystallisation ofjce, and each 

 column as it tries to develop itself is interfered with by its neighbour, 

 and the resulting slab of ice is made up of elementary prisms 

 crowded together, but preserving parallelism of crystallographic 

 axis. 



Characteristics of an Advancinij Glacier. — In the month of August 

 1895 I visited the valley of Chamounix, and had the good fortune 

 to find that the Glacier des Bossons was advancing. This was 

 particularly noticeable when crossing the moraine on its eastern flank. 

 The ice was everywhere undermining it, and keeping it generally on 

 the move. On the western side, where the glacier terminated in 

 several points, these acted like ploughshares, in turning over the 

 detritus in front of them. The glacier stream escaped from an 

 Antrum, having a remarkably small entrance, about 2 metres high 

 and 3 metres wide. 



In pursuance of certain experiments which I was making regard- 

 ing the melting of glaciers, I entered the antrum and bored a nearly 

 vertical hole, about 12 centimetres deep and 14 centimetre wide, in 

 the ice of the eastern ^^■all. It was within a metre of the entrance, 

 but so situated that the water produced by the melting of the 

 surface ice, which poured over the entrance, could not reach it. 



Although everywhere there appeared to be melting, the hole 

 remained empty and dry ; even ttie snow-turnings which remained 

 in the hole were quite dry. It was still perfectly dry when I left the 

 glacier at 6 p.m. When I visited it agani the next day at 3.45 p.m. 

 it was still perfectly dry. The stream flowing out of the antrum 

 was so voluminous that it was impossible to explore it that afternoon. 

 The next day, however, the 15th, at 11 a.m., the volume of water 

 was small, and it was possible to penetrate into the antrum. It ran 

 into the ice in a straight hue for '11 metres, and terminated in a 

 rock 2 metres high by o metres broad, which filled the whole area of 

 the cavern. 



Grooving of Ice by Rock. — While making these measurements, 

 my attention was arrested by an appearance on the roof of the cave, 

 close to where the top of the rock bore against the ice. From the 

 line of contact, and for a distance of about half a metre towards the 

 entrance, the ice was deeply scored and grooved. At first I could 

 hardly believe it ; but there was no doubt about it. Although I 

 had often heard of glacial action, the idea of glacial reaction had 

 never occurred to me, still less had I ever expected to witness 

 it. The experience that in an auger hole bored in the ice within 

 a metre of the entrance, and in very hot weather, the delicate 

 ice-turnings which were left in it remained unmelted for at least 

 twenty-four hours, made it no longer wonderful that the surface of 

 the ice at a distance of 20 metres further from the entrance, should 

 remain unmelted lono^ enous'h to show the effect on it of the rock 

 over which, on evidence external to the glacier, it was passing with 



