66 .: SEVENTH REPORT— 1837. 
the ice on which it rests, and sinks down, forming in the substance of 
the ice a tube of an enormous depth; one found by Mr. Mallet in 
1831 having a depth of 70 feet and a diameter of 3 feet. This tube 
gradually enlarges and becomes filled with water, until the pressure of 
the column of water overcomes the lateral cohesion and splits the mass 
into two or more pieces.—The curvilinear form of the crevice is next 
explained. As the waters proceeding from the melting of the under 
surface of the ice will coalesce towards the centre of the bed of the 
glacier, or the lowest point of its sloping surface, so will the centre be 
raised more and descend more than the sides ; and, in consequence, the 
central part of the whole crevice descending most, it becomes convex 
downwards. 
Mr. Mallet then entered on a discussion of those accumulations of 
stony debris called “Moraine,” which are to be found on all the glaciers, 
and most remarkably on the glacier of Rosboden on the Simplon. These 
are ridges of loose materials arranged parallel to the motion of the gla- 
cier, or across the ice crevices. The detritus proceeding from the pre- 
cipices which flank the glacier valley is continually falling and mixing 
the snow with gravel and rocks; and, as the summer heat melts the 
winter snow, all this suspended matter sinks down to the surface of the 
ice, and by the force of torrents sweeping over the ice is formed into 
those ridges which lie nearly parallel to the line of motion of the whole 
glacier. In these ridges, the centre is many feet deep; and as this 
thickness protects the ice below from the heat of summer, an elevated 
wall of ice is formed, the uncovered snow on each side being melted 
down, so that these ridges of stones stand upon hills of ice sometimes 
25 feet above the general surface ; and as the centre of the glacier sinks 
more than the sides, these hills have a natural tendency to topple over 
and discharge their load of stony matter towards the centre: hence the 
greatest deposits of moraine are nearest the axis of the whole glacier, 
and these act as checks to its too rapid melting, without which it is 
probable some of the greater glaciers would have been entirely melted 
through, and the mechanism of their motion destroyed. On the prin- 
ciples here laid down, the motion of the glaciers is most rapid after a 
severe winter, and vice versd. The constant descent of a glacier over 
its bed must abrade and smooth the surface of the rock, just as if it 
had been the bed ofa torrent; and it may therefore be possible to trace 
in such marks the former existence of glaciers now totally melted 
away. - 
On the Results of Trials which had been made for Water in the Desert 
between Suez and Cairo. By Marquis Spineto. 
This search had been conducted by M. Albert Gingbery, an en- 
gineer and mineralogist, and had proved successful, five wells having 
now been established on that route. In these trials the water was 
found at the depth of 14 feet, filtering through a calcareous rock, and 
in a stratum of clay or marl. The results of several other borings 
ina 
