Mr. R. M. Deeley on Glacier- Grains. 45o 



are of considerable amplitude, the equations of motion cannot 

 be regarded as sensibly linear ; and accordingly it is to be 

 expected that if two sources of sound are brought closer to- 

 gether, the intensity of the difference-tone will increase. I 

 have used two stopped organ-pipes of white metal giving the 

 notes e' and g' \ the difference-tone being consequently C. The 

 pipes are connected to a well-weighted organ-bellows by 

 flexible rubber tubes, and the distance between them can be 

 varied at will from a few feet to a couple of inches (the walls 

 of the two pipes being then in contact). It is best for the 

 listener to be stationed in a distant room, so that the sound 

 which reaches him is only of moderate intensity, while the 

 comparatively small distances through which the pipes are 

 moved does not appreciably affect the sounds which they indi- 

 vidually send to his ear. The bellows being filled, the sound- 

 ing pipes are held alternately far apart and near together, 

 and each time, as they nearly approach one another, the dif- 

 ference-tone Cx is heard to boom out with greatly increased 

 intensity. From this, I would suggest, we are to infer that 

 the difference-tone has a real objective existence. 



(Further experiments have not confirmed this result. Even 

 Prof. Pucker's very sensitive arrangement of interference- 

 bands failed to show any objective difference-tone from the 

 two organ-pipes, suitably tuned. An attempt will be made 

 to deal with the subject more fully in a subsequent piper.) 



XLIV. Glacier- Grains. 



To the Editors of the Philosophical Magazine. 



10 Charnwood Street, Derby, 

 Gentlemen, April 3, 1895. 



IN 1888 I communicated to the February No. of the Phil. 

 Mag. a short paper on glacier motion. Since then I have 

 had an opportunity of examining, in company with Mr. G. 

 Fletcher, F.G.S., the structure of some of the largest Swiss 

 and Norwegian glaciers. The results of our investigation 

 are given in a paper printed in the April number of the 

 Geological Magazine for the current year. 



In it we show that the small granular particles of ice 

 resulting from the partial melting and refreezing of the snow, 

 and also the minute crystal particles collected during frosty 

 sunless days, in course of time, when they have become 

 welded by pressure into a compact mass, undergo a striking 

 change. The greater number of the granules and crystalline 

 particles disappear, the molecules composing them going to 

 build up a comparatively small number of large crystalline 



Phil. Mag. S. 5. Vol. 39. No. 240. May 1895. 2 H 



