Scieittific Intelligence — Meteorologi/. 381 



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

 two united rivers would do. 



The author nieasux-ed 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 1.356 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 tho 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 

 origin. 



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, th*t in nearly every instance 

 the velocity of the glacier, during any period of days, has a refe- 

 rence to the temperature of the same period. If the thermometer 

 fell, the glacier advanced slower, and vice versa. It is not, how- 

 ever, to be inferred that at the same external temperature the velo- 

 city 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 

 contrary, he supposes that though its velocity is less than in summer, 

 it still bears a considerable proportion to it. 



On the 20th March 1843, Professor Forbes read a memoir to the 

 Royal Society of Edinburgh, on the structure of glaciers and the 

 cause of their motion. 



With reference to his former paper of the 27th February, the 

 author stated that he had received a most satisfactory confirmation 

 of his opinion respecting the motion of glaciers in winter. Fi'oui 



