226 Professor Forbes on the Leading Phenomena of Glaciers. 



monstrated beyond a doubt, that, at least, any transient im- 

 pression of cold is quite incapable of converting the infiltrated 

 water into ice at any depth in the glacier. 



2. At the same time that the preceding observations were 

 made, the rate of motion of the glacier was carefully observed ; 

 for I concluded, as a matter of certainty, that, if the dilata- 

 tion theory were true, a sudden frost succeeding wet weather 

 must inevitably cause the glacier to advance far more rapidly 

 than in summer, or, indeed, at any other season ; for there 

 could never possibly be more water to be frozen, nor could cold 

 ever act with more energy than at the time in question. What 

 the facts were, we have already seen in the seventh chapter, 

 where it appears, both from the tables and figures, that the 

 progress of the glacier was retarded during the cold weather 

 which prevailed from the 20th to the 25th September, and 

 that it readvanced when the thaw had taken place some days 

 later. 



3. The motion of the glaciers during winter, established in 

 the same chapter, is directly contrary to the conclusions in- 

 variably drawn by the glacier theorists from their supposed 

 immobility ; since they consider, that, while the glacier is com- 

 pletely frozen, and has no alternations of congelation and thaw, 

 there can be no dilatation. 



4. My experiments shew, that the motion of a glacier during 

 the day and night is sensibly uniform, which is contrary to the 

 same view. 



5. The rate of motion of the glacier at different parts of its 

 length has been shewn to be by no means such as the expan- 

 sion of an elongated body, supported at one end, and pushed 

 along its bed, would occasion. 



6. The advocates of the theory of dilatation have rightly 

 maintained, as a consequence of the theory, that the ice will 

 expand in all directions, and consequently upwards, that being 

 the direction in which the resistance is least of all. They 

 thence conclude, that, whilst the ice wastes by melting at the 

 surface, the surface will be raised by the inflation of the in- 

 terior mass by the expansion of freezing water, and that its 

 absolute level will thus be maintained, or will even rise, not- 

 withstanding the daily waste. They profess to have made 



