15. 308 Anticipations of Rendu confirmed by Agassiz and Forbes; analogies with Liquid Motion established by Forbes; his Measurements in 1842; measurements in 1844 and 1846; Measurements of Agassiz and Wild in 1842, 1843, 1844, and 1845; Agassiz notices the "migration" of the Point of Swiftest Motion; true meaning of this observation; Summary of contributions on this part of the question 16.--Forbes's Theory. 311 Discussions as to its meaning; Facts and Principles; definition of theory; Some Experiments on the Mer de Glace to test the Viscosity of the Ice 17.--The Crevasses. 315 Caused by the Motion; Ice Sculpture; Fantastic Figures; beauty of the crevasses of the highest glaciers; Birth of a crevasse; Mechanical Origin; line of greatest strain; Marginal Crevasses; Transverse Crevasses; Longitudinal Crevasses; Bergschrunds; Influence of Flexure; why the Convex Sides of glaciers are most crevassed 18. 325 Further considerations on Viscosity; Numerical Test; formation of crevasses opposed to viscosity 19.--Heat and Work. 328 Connexion of Natural Forces; Equivalence of Heat and Work; heat produced by Mechanical Action; heat consumed in producing work; Chemical Attractions; Attraction of Gravitation; amount of heat which would be produced by the stoppage of the Earth in its Orbit; amount produced by the falling of the Earth into the Sun; shifting of Atoms; heat consumed in Molecular Work; Specific Heat; Latent Heat; 'friability' of ice near its melting point; Rotten Ice and softened Wax 20. 334 Papers presented to the Royal Society by Professor Forbes in 1846; Capillary Hypothesis of glacier motion; hypothesis examined 21.--Thomson's Theory. 340 Statement of theory; influence of Pressure on the Melting Point of Ice; difficulties of theory; Calculation of requisite Pressure; Actual pressure insufficient 22.--Pressure Theory. 346 Pressure and Tension; possible experiments; Ice may be moulded into Vases and Statuettes or coiled into Knots; this no proof of Viscosity; Actual Experiments; a sphere of ice moulded to a lens; a lens moulded to a cylinder; a lump of ice moulded to a cup; straight bars of ice bent; ice thus moulded incapable of being sensibly stretched; when Tension is substituted for Pressure, analogy with viscous body breaks down 23.--Regelation. 351