410 



Velocity. 



T i ( 1.000 



Lower part, 1 0.770 



Middle do., 0.479 



Higher do., 0,674 



II. The Glacier du Geant moves faster tliat the Glacier de Lechaud 

 in the proportion of 7 to 6. 



III. The centre of the glacier moves faster than the sides. When 

 two glaciers unite, they act as a single one in this respect, just as 

 two united rivers would do. 



The author measured the velocities at different places in the 

 breadth of the glacier, and it was found to increase towards the centre. 

 The following are the numerical results, assuming the motion of the 

 ice near the edge as the standard or the unit of reference. 



Side. Centre. 



1.000 1.332 1.35G 1.367 



IV. The difference of motion of the centre and sides of the gla- 

 cier varies (1) with the season of the year, and (2) at different parts 

 of the length of the glacier. 



1. From the observations made, the author concludes, that " the 

 variation of velocity diminished as the season advanced ; and that it 

 was proportional to the absolute velocity of the glacier at the same 

 time." 



2. The variation of the velocity with the breadth of the glacier is 

 least considerable in the higher parts of the glacier, or near its 



origm. 



V. The motion of the glacier generally varies with the season of 

 the year and the state of the thermometer. 



Perhaps the most critical consideration of any for the various 

 theories of glacier motion is the influence of external temperature 

 upon the velocity. It is shewn in this paper, by a direct numerical 

 comparison, and by projected curves, that in nearly every instance 

 the velocity of the glacier, during any period of days, has a reference 

 to the temperature of the same period. If the thermometer fell, 

 the glacier advanced slower, and vice versa. It is not, however, to 

 be inferred that at the same external temperature the velocity will 

 always be the same ; only at any season, the change will always be 

 in the same direction, and governed by the thermometer, though not 

 always the same in amount. 



The author also deduced from various indirect considerations, that 

 it is very improbable that the glacier stands still in winter. On the 



