1846.] RESULTS OF BALMAl's MEASUREMENTS. 127 



these holes were renewed from time to time as the surface of 

 the ice wasted. A staff of wood, 5j feet long, was stuck in 

 each, which projected sufficiently above the snow (which never 

 appears to have exceeded 2J feet deep on the glacier) to make 

 it visible at all seasons. During winter the staves were frozen 

 into the ice, and the waste being small, the holes did not re- 

 quire renewal. Two marks are then made of a permanent 

 kind ori the rocks of the moraine, or two staves driven in, or a 

 distant object on the farther side of the glacier was observed, so 

 as to mark out sufficiently a line transverse to the glacier, the 

 prolongation of which passes over the hole in the ice when first 

 made ; and the advance of the hole in the ice beyond this fixed 

 visual line marks the progress of the glacier. The want of a 

 theodolite is supplied by directing the eye past a plumb-line 

 suspended over the fixed mark on the moraine nearest to the 

 glacier, the eye of the observer being over the farthest mark. 

 As the spaces moved over were in most cases considerable, an 

 error of a few inches, or even a foot, is not important to the 

 result. The progress was in every case determined by means 

 of a line marked with English feet and inches, left by me at 

 Chamouni on purpose. 



The results were communicated to me regularly by letter at 

 intervals of a few weeks during the whole year, and all questions 

 asked and explanations required by me were answered by return 

 of post. 



Those who may look with suspicion upon observations made 

 in a remote place by a peasant of the better class, though they 

 may not partake of my security in the results from knowing the 

 character of the individual, will, I believe, have their doubts 

 removed by the internal evidence of this important series of 

 observations, which even a philosopher could not have in- 

 vented, and which, it will be seen, are confirmed by data of 

 quite another kind, over which the observer could have no 

 control, I mean the Meteorological Registers of Geneva and 

 St. Bernard. 



The following Table contains, in a condensed form, the 



