"Report of the Besearches of M. Agassiz. 149 



was towards the north. With these data he set to work to ac- 

 count for this particular arrangement, which he explains in 

 nearly the following terms : — When a little gravel, from 

 any cause, accumulates behind an elevation upon the surface 

 of a glacier, it by degrees sinks down in the ice, and this pro- 

 duces a small hollow, or a miniature kind of basin. But as 

 gravel absorbs much more caloric than ice, it follows, that it will 

 be on the side where the sun's rays strike with the greatest 

 intensity, and for the longest time, that this basin will most 

 enlarge, and the gravel sink the deepest. Now, this side must 

 necessarily be the northern, and hence the reason that every 

 basin has its convexity turned to the north. 



These small basins prove not a little useful to the moun- 

 tain traveller, in affording him facilities for piloting himself 

 with considerable certainty in spite of fogs, and even of ascer- 

 taining the hour of the day, however obscured the sun may 

 be. For these objects, he has only to place his pole, or 

 walking- staff, over the cavity, in such a way that it touches, 

 on one side, the summit of the small icy elevation, and, on 

 the other, the summit of the arc, and the line which his staff 

 forms, will lie precisely north and south. A line at right 

 angles to this, will consequently lie east and west. The meri- 

 dian being thus known, it will be easy for him approximately to 

 iearn the hour, from the angle which the sun forms with the 

 meridian line. It is, accordingly, on account of the facilities 

 which these small excavations present on this point, that we 

 designated them Meridian cavities. In Germany, they are 

 called Kellerldcher^ in honour of our friend M. Keller. 



Observations upon Temperature. — The experiments upon 

 temperature were those which M. Agassiz prosecuted most 

 zealously during his sojourns in the years 1841 and 1842. 

 Not only were the variations of the external temperature 

 made the subject of daily observations, often repeated from 

 hour to hour, but he was especially anxious to observe what 

 was the state of the temperature in the interior of the gla- 

 cier. We have, on a former occasion, remarked, that many 

 shafts or bores were cut mth this object in view, to the 

 depths, one of 100 feet, and another of 50, and several to 

 the depths of 15, 20, and 25 feet. The bore to the depth 



