[10.]—Motion of the Mer de Glace.[275]

The Theodolite; mode of measurement; first line; Centre Point not the quickest; second line; former result confirmed; Law of Motion sought; the glacier moves through a Sinuous Valley; effect of Flexure; Western half of glacier moves quickest; Point of Maximum Motion crosses axis; Eastern half moves quickest; Locus of Point of Maximum Motion; New Law; Motion of the Géant; motion of the Léchaud; Squeezing of the Tributaries through the Neck of the valley at Trélaporte; the Léchaud a Driblet

[11.]—Ice Wall at the Tacul,—Velocities of Top and Bottom.[289]

First attempt by Mr. Hirst; second attempt, stakes fixed at Top, Bottom, and Centre; dense fog; the stakes lost; process repeated; Velocities determined

[12.]—Winter Motion of the Mer de Glace. [294]

First line, Above the Montanvert; second line, Below the Montanvert; Ratio of winter to summer motion

[13.]—Cause of Glacier Motion,—De Saussure's Theory. [296]

First attempt at a Theory by Scheuchzer in 1705; Charpentier's theory, or the Theory of Dilatation; Agassiz's theory; Altmann and Grüner; theory of De Saussure, or the Sliding Theory; in part true; strained interpretation of this theory

[14.]—Rendu's Theory.[299]

Character of Rendu; his Essay entitled 'Théorie des Glaciers de la Savoie;' extracts from the essay; he ascribes "circulation" to natural forces; classifies glaciers; assigns the cause of the conversion of snow into ice; notices Veined Structure; "time and affinity;" notices Regelation; diminution of glaciers réservoirs; Remarkable Passage; announces Swifter Motion of Centre; North British Review; Discrepancies explained by Rendu; Liquid Motion ascribed to glacier; all the phenomena of a River reproduced upon the Mer de Glace; Ratio of Side and Central velocities; Errors removed