Rates of Motion. 

 Relative Daily Motions, D 2 heing = 1. 



139 



It will be seen that both the absolute and relative motions 

 were markedly greater in 1846 than in the previous years ; 

 and that this also agrees with the annual motions at station 

 C given above. 



A block, on the ice opposite Les Fonts (between Montanvert 

 and the Angle), marked with the letter P on the 18th Septem- 

 ber 1843, moved 486 feet from that date to 9th August 1844 

 (or 331 days), being 17"62 inches daily, or 536 feet annually. 

 The same block re-examined on the 16th July 1846, had 

 moved 776 feet since the 9th August 1844, or only 13-2 inches 

 daily, or 402 feet annually. The retardation must be attri- 

 buted to the block having been thrown almost upon the mo- 

 raine, as happened to the block D 7 under similar circum- 

 stances.* To avoid such a mischance again, I marked the 

 position of a fine block now near the centre of the Mer de 

 Glace opposite to Les Fonts. It was painted with the letter 



V on both sides, and its position determined with reference 

 to a point on the pathway between the two Fonts, to which 

 it was exactly opposite on the 30th July 1846, when the ob- 

 servations were made. The mark is a cross with the letter 



V on a small granite block solidly placed on the left of the 

 pathway. The block on the ice is 760 feet distant from the 

 west shore. 



By reference to my Eighth Letter, published in this Journal, 

 and to the fuller details in the London Philosophical Trans- 

 actions for 1846, on the Plasticity of Glacier Ice, it will be 

 recollected that I made observations at a station marked 

 Q between the Angle and Trelaporte. This station was 300 

 feet from the west moraine. The following observations 

 were made last summer in the same part of the glacier, at a 

 distance of 553 feet from the moraine : — 



♦ See Fifth Letter on Glaciers. 



