124 VISCOUS THEORY OF GLACIER MOTION. [1846. 



Again, being enabled to repeat the measures in 1844, I 

 found the advance 



From the 12th of September 1843, to the 19th of 



August 1844 (342 days), . . . . 270 feet. 



Proportional motion for 365 days, . . . 288*3 feet. 



Mean daily motion, . . . ... . .." 9*47 inches.* 



In the case of the block D 7, 1 was less fortunate. It was 

 very near the western side of the glacier, and though not thrown 

 up on the shore, yet the ice on which it rested got in some 

 manner so embayed or entangled, that though its motion had 

 been steadily watched during the winter of 1842-43 by my able 

 assistant, Auguste Balmat, it had scarcely moved since his 

 last observation on the 8th of June 1843, when I visited it in 

 September of the same year. It must be presumed that it had 

 been much retarded previously, and hence it is clearly inadmis- 

 sible to infer a proportional motion for the portion of the year 

 when it had not been observed, as I did in the Postscript at 

 the end of the first edition of my Travels, whilst in ignorance 

 of the then unsuspected retardation. The motion actually 

 observed was 432 feet in 322 days, being at the rate of 483 

 feet per annum, or 15*88 inches per day. This is, therefore, 

 undoubtedly below the true measure of the annual motion of the 

 side-part of the glacier somewhat in advance of the Chalet of Mon- 

 tanvert (see the position of D 7 in the Map). It may at least be 

 of some service as an inferior limit of the annual motion there. 



In 1843 I fixed approximately the position of a block marked 

 P, higher up the glacier than the Montanvert, and near its left 

 bank, exactly opposite the spot called Les Ponts. The obser- 

 vation, being repeated the ensuing year, gave a motion of about 

 486 feet (the nature of the observation did not admit of the 

 same accuracy as at station C) from the 13th of September 1843 

 to the 9th of August 1844, or 331 days, being at the rate of 



536 feet per annum, 

 or 17'62 inches per day. 



* [The like annual motion for the interval 1844-46 was 323'8 feet, or 10'65 

 daily inches ; and for the interval 1846-50, 328'8 feet, or 10'81 inches daily. See 

 13th and 1 6th Letters below.] 



