1850.] STATIONS C AND V ON THE MEB DE GLACE. 221 



earliest points whose position was ascertained by me in 1842. 

 Its daily motion was watched by me during that summer,* and 

 its annual motion was ascertained by renewed observations in 

 1843, 1844, 1846, and again this year. I measured the dis- 

 tance along the ice from the original position of the " Pierre 

 platte" on the 27th June 1842 (ascertained by reference to 

 fixed marks on the rocks) to its position on the 12th July 1850. 

 and found it to be 2520 feet. But of this distance, 1212 feet 

 had been travelled at my previous observation on the 21st July 

 1846, leaving 1308 feet during the last four years against 1212 

 in the first four. When more accurately stated and compared, 

 the mean annual and daily motions will stand as follows : 



1842-3. 1843-4. 1844-6. 1846-50. 



Daily motion, in INCHES, -8'56 9'47 10'65 1081 



Annual motion, in FEET, 260'4 288'3 323'8 328'8 



We cannot infer, with absolute certainty, that the slight increase 

 of velocity here noticed since 1844 is due to a change in the 

 conditions of the glacier (although I believe that the recurrence 

 of several snowy seasons and the very marked increase of the 

 volume and extent of the glacier during these years would pro- 

 duce such an effect), because it has moved nearly half a mile 

 from its position when first observed, and the part of the glacier 

 on which it now lies may be subject to different accelerating 

 and retarding causes. 



It is mentioned in my Thirteenth Letter, page 4, that I 

 marked a fine solitary block towards the centre of the Mer de 

 Glace, opposite " Les Fonts," with the letter V in 1846, and 

 that I took angles for fixing its place with reference to the ad- 

 jacent rocks. It was then about 760 feet distant from the west 

 bank. I had little difficulty in recognizing the block in 1850, 

 although it had travelled a great distance, and was considerably 

 lower than the Montanvert. It had preserved its parallelism 

 to the shore, for I found it at almost the same distance from 

 the west bank as at first ; and by measuring carefully along the 

 side of the glacier, I estimated its progress in four years, from 



* Travels in the Alps of Savoy, 2d edition, p. 139, 140. 



