recently made on the Glacier of the Aar, 401 



is, that the liquid is not distributed uniformly through the whole mass, 

 but only infiltrates through the capillary fissures. 



In examining in detail the structure of the ice, M. Agassiz noticed, 

 round the bubbles of air it contains, bubbles of water of various forms, 

 which can only be distinguished in certain positions opposite the light. 

 The presence of this liquid water round bubbles of air in great masses of 

 ice is a very extraordinary fact, and is considered by M. Agassiz as a 

 phenomenon of diathermansie, the more especially as these bubbles be- 

 come larger and more distinct when the ice has been for a long time ex- 

 posed to the air. 



M. Agassiz was anxious to know exactly the quantity of air contained 

 in the various modifications of the ice of the glacier. M. Nicolet took 

 charge of the experiment, and obtained the following mean results : — 



500 grammes of snow passing into neve', 32 cubic centimetres of air. 



ice formed under that snow, 0.9 



white ice, . , . 7.5 



blue ice, . . , 0.5 



blue ice of the gallery, 0.9 



M. Agassiz has ascertained, that the nocturnal radiation of the ice is 

 very considerable. It is only in stormy and snowy nights that the tliermo- 

 metrographs placed at the surface of the glacier and of the moraine do not 

 differ in their indications, whereas in clear nights the thermometer always 

 descends 1 or 2 degrees cent, lower on the glacier than on the moraine. 

 M. Hugi asserted, that the temperature of the moraine is always much 

 lower than that of the glacier; observations continued for three weeks 

 have proved the contrary. 



It has been long said, that the ice of the interior of the glacier is com- 

 pletely free from earthy matter, because it rejects every thing which falls 

 into its crevasses. This assertion is by no means correct, as the following 

 will show : M. Agassiz melted a quantity of ice raised from a depth of 20 

 feet under the surface of the glacier, and which yielded 27 litres of water; 

 and he found that it contained 64 grammes of fine sand. Proceeding on 

 theie data, we may calculate approximatively the amoimt of sand con- 

 tained in the glacier of the Aar (whose ice seems extremely pure), at the 

 enormous quantity of 2,560,000 kilogrammes. 



The mode of disaggregation of the ice at the surface of the glacier has 

 also been the object of continued observation. In proportion as the at- 

 mosphere acts on the glacier, after the melting of the snows of the cold 

 season, which disappear completely in May and June, the ice becomes 

 porous, but does not decompose uniformly. At first it is generally white, 

 wherever tlierc is no accumulation of fragments of rock and of dust to pro- 

 tect it from the action of the sun ; but in proportion as it imbibes the water of 

 the summer rains, its tint becomes more and more blue. These differences 

 of colour are maintained at all parts of the glacier where the form of the 



