238 Intelligence and Miscellaneous Articles. 



the moment of the liquefaction of carbonic acid, since that liquid 

 does not mix with water. Experiment shows that the decrease of 

 the surface-tension, becoming slower with the increase of pressure, 

 tends also towards a certain limit, which at 0° is reached under the 

 pressure at which the liquefaction of carbonic acid takes place ; at 

 that instant the surface-tension of the water is reduced to about 

 one half *. 



Bisulphide of carbon, which also does not mix with liquefied car- 

 bonic acid, behaves in a similar manner in contact with that gas. 

 The decrease of its surface-tension also takes place at 0° much 

 more quickly than at a higher temperature. It becomes slower, 

 and ceases under the pressure of liquefaction of the gas. 



In my next Note I will show that the phenomena present them- 

 selves under a different form as soon as we have to do with a liquid 

 that mixes in all proportions with liquefied carbonic acid. — Comptcs 

 Benclus de VAcademie des Sciences, Aug. 7, 1882, t. xcv. pp. 284-287. 



ON THE STRUCTURE AND MOVEMENT OF GLACIERS. 

 BY M. F.-A. FOREL. 



M. F.-A. Forel, of Morges, Switzerland, has recently published 

 (Bill. Univ. in., vii. p. 329) an important memoir upon glaciers, 

 embodying the results of observations by himself and M. Ed. 

 Hagenbach-Bischoff, with a discussion of these results and also of 

 those obtained by other observers. His argument rests plainly 

 upon the well-attested fact that glacial ice has a distinctly crystal- 

 line granular structure, the mass being composed of a confused 

 agglomeration of individual crystals, each optically distinct — and, 

 moreover, that the size of these crystalline grains increases from 

 the upper margin of the glacier at the limit of the neve, where they 

 have the size of a hazel-nut, down to the middle part, where the 

 size is that of a walnut, and further down to the extremity, where 

 they are as large as a hen's egg. For example, at the lower extre- 

 mity of the Aletsch glacier, or that of the Bhone, the grains have a 

 diameter of 7 or 8 centim. In regard to this gradual increase in 

 size of the individual crystals, the author remarks that two suppo- 

 sitions are possible : either the growth of some grains must go on 

 at the expense of others less favourably situated, one gaining what 

 the next loses, and absorbing as much heat as is disengaged by the 

 crystallization ; or each grain increases in size by means of the 

 water which reaches it from above from the surface of the glacier. 

 Of these two hypotheses, the first is rejected, on the ground that, 

 wherever observations have been made, they have shown the grains 

 to be all of sensibly the same size in the same region, and not to 

 be some small, others large, as this explanation would require. 



Accepting provisionally the second hypothesis, the author re- 

 marks that for the increase in volume of the crystals thei-e are 

 needed water, cold, and favourable conditions. About the last point 

 nothing is definitely known ; but the others admit of further dis- 



* The case in which one of these two liquids is superposed to the other 

 does not come within the scope of this communication. 



