402 Obaer cations recently made on the Glacier of the Aar. 



surface causes constant currents of water during the day, or at least a larger 

 supply of water after heavy rains. This contrast is particularly striking 

 wlien a violent fall of rain occurs after a succession of several fine days ; 

 the glacier, wliich was rendered white by the warm days, then becomes 

 at once distinctly blue. When the heat continues for a long time, the 

 whole surface becomes disaggregated in various ways ; the white bands 

 assume the aspect of a granular snow, perfectly similar to the neve, where- 

 as the blue bands are decomposed into angular fragments, and the por- 

 tions which consist of intimately blended blue and while ice assume a 

 structure similar to that of pumice. Another effect of the superficial de- 

 composition of the ice, is the disjunction of the blue and white bands, 

 between wliich are formed very elongated longitudinal fissures, that 

 penetrate more or less deeply. These fissures frequently give rise to dis- 

 locations resembling parallel faults ; the whole glacier sometimes ac- 

 quires, in consequence of these dislocations, the appearance of a great 

 book placed on its back, and so far opened as to cause the leaves to slide 

 on one another. 



. M. Agassiz next speaks of. a curious phenomenon which came under 

 his observation. At half- past four in the evening the workmen were 

 boring, when the glacier began to crack under their feet, and to disen- 

 gage a large quantity of air-bubbles. Crevices of some lines in breadth 

 soon presented themselves at the surface. After the lapse of some mi- 

 nutes a crack was lieard, resembling simultaneous detonations of fire- 

 arms in platoon firing, accompanied by single reports, and commotions 

 similar to those caused by an earthquake. The glacier really trembled. 

 A little afterwards, about seven o'clock, the bore, which was 130 feet 

 in depth and 6 inches in diameter, and full of water, was emptied in 

 a few minutes — a fact proving that these crevices, although very nar- 

 row, penetrated to great depths. At half-past eight the shocks still con- 

 tinued, and they were heard during the night. M. Agassiz counted a 

 dozen of crevices, of which the largest was about an inch and a-half 

 wide. A circumstance worthy of notice is, that they all succeeded each 

 other from above downwards, following the slope of the glacier. 



With the viewing of obtaining information regarding the temperature 

 of the glacier during winter, M. Agassiz had last autumn introduced two 

 of Buntcn's thermometrographs into bores of 12 and 24 feet in depth. 

 (See this Number of the Journal, p. 277.) But notwithstanding the pre- 

 cautions which had been taken, the one alreadj^ brought up has not af- 

 forded a correct result. It was hoped that the other would be extracted 

 by means of a current of water. 



In conclusion, M. Agassiz announces the return of MM. Desor and 

 Escher de la Linth from a successful ascent of the Schrcckhorn, whose 

 summit rises to the height of 4082 metres, and had not previously been 

 reached. The hygrometer indicated 43 at + 4°. C. (39°. 2 F.)— (////t- 

 stitut, No. 453). 



