150 Beport of the Besearches ofM. Agassiz. 



of 200 feet, whereby we had hoped to reach the bottom, in 

 the year 1842, was also exclusively used for this purpose, 

 during the last eight days of our sojourn. Every evening 

 we introduced a self-registering thermometer to the bottom 

 of each of these bores, respectively 200, 100, 50 feet deep, 

 and occasionally into a fourth 20 feet deep. There they were 

 allowed to remain during the night, every care being taken, 

 by means of such things as sheep-skins, blankets, &c. covered 

 over again with plates of ice, to prevent the ingress of the 

 external cold. Next morning, usually about six o'clock, 

 MM. Agassiz and Girard went to examine the thermometers, 

 both those on the surface, and the others in the ice. These 

 experiments were repeated in 1841, for a period extending 

 to nearly six weeks, and in 1842, during two consecutive 

 months. Often also we reintroduced the instruments, leaving 

 them during the day, and examining them in the evening, before 

 the temperature fell below 32° F. We will not here, of course, 

 enumerate the details. Suffice it to state, that the general 

 result has been confirmatory of what the observations of the 

 year 1840 had shewn, namely, that the temperature is nearly 

 constant in the interior of the glacier. We have scarcely 

 seen it oscillate beyond the limits of three-tenths of a degree ; 

 in other words, the self-registering thermometers have never 

 indicated a higher temperature than 32° F., or a lower tempera- 

 ture than - 0°.3 (31°.46 F.) and this when the external 

 temperature was as low as •— 5° (23° F.), and even 6° G. 

 (21°. 2.) Generally, the index stood precisely at 32° F. 



But M. Agassiz was unwilling to limit himself to daily ob- 

 servations ; for however important these might be, they sup- 

 plied the temperature of the glacier only at a determinate 

 epoch, namely, at that corresponding to the hottest season of 

 the year. But where were the grounds for supposing that the 

 temperature was the same at the other seasons of the year ? 

 And admitting that the night cold did not exercise any 

 marked influence upon the interior of the glacier, did this 

 authorize us to conclude, that the colds of winter, so severe 

 and prolonged in these high regions, have not a greater in- 

 fluence upon the temperature of the glaciers I These objec- 

 tions had been foreseen in 1841, and M. Agassiz has publish- 



