“It will be recollected that a remarkable stone called ‘La pierre platte,’ was one of the earliest points on the Mer de Glace at Chamouni 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 distance 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.