Scientific Intelligence — Geology, 397 



gai'ding the origin and progress of glaciers, are only heard in the far 

 distance, and since the general conviction that Agassiz's unsuccess- 

 ful attempt to live three summers on a glacier, and all the care and 

 labour expended there, have led to no other result, than to confirm 

 still more the wise considerations and deductions of Saussure, and to 

 prove that the faculty of extended generalization, which depends on 

 few but sure observations, leads sooner and more directly to the 

 truth than all the instruments we may heap together, without using 

 them with proper precautions. Even the echo, still faintly repeated 

 from the other side of the Atlantic, will in a short time cease. 

 "When we question the maps of the Swiss Alps, the mountains in the 

 Tyrol, the Norwegian glaciers, the few seen in the Pyrenees, the 

 magnificent vicinity of the sources of the Ganges and Jumna, — 

 everywhere the same law appears, namely, " That glaciers only form 

 on mountains that rise above the limits of perpetual snow, and spread 

 out in this region ; the origin of such glaciers must be sought in de- 

 pressions, — wide basins of snow. They never originate on the open 

 rocks far from large masses of snow. From these wide pots of snow, 

 the icy mass proceeds down in deep valleys, perhaps even to inha- 

 bited places, where the temperature of the air sets limits to its far- 

 ther progress, and where the portion destroyed by melting must be 

 continually and rapidly renewed from above.' ' From these essential 

 conditions in the formation of glaciers it evidently results, that the 

 cause of their progress and sliding down into the valleys must be 

 soughtj either altogether, or at least diiejiy towards their origin, 

 and above the snow-line, never in the ice masses themselves, which 

 in this respect are altogether passive. In this upper region the pres- 

 sure of the connected ice masses operates, exactly as the pressure on 

 the Rossberg has pushed down a whole stratum of the mountain, de- 

 stroyed it, and covered half a canton with the giant fragments ; and 

 this pressure is not destroyed in its progress, but increased until the 

 temperature and smaller declination of the valley are able to counter- 

 balance the pressure of the mass. No glacier continues to move 

 when the bottom of the valley on which it rests has a less inclina- 

 tion than 3° (Elie de Beaumont.) No doubt large extended masses 

 of snow often appear in confined valleys below the snow line ; they 

 may be even changed into vaults of ice as is so beautifully seen in 

 the ice-chapel not far from the Bartholomseus lake at Berchtesgad ; 

 only these never move ; they fill no valley like a long ribbon, like a 

 frozen cataract, — for they want the pressure from above, the only 

 thing that can move them downwards into the valley. — Description 

 of Bear Island, vide Quarterly Journal of the Geological Society, 

 No. 11, p. 51. 



3. Mark cut on a rock cliff at the mean level of the Sea, with the 

 view of determining the secular Variation of the relative level of tfic 

 Sea and Land. — My principal object in visiting Port Arthur was 

 to afford a comparison of our standard barometer with that which 



