Prof. Tyndall on some Phjsical Proj)erties of Ice. 353 



I think the following new facts have been established in the 

 foregoing paper : — 



1. The interior of a mass of ice may be melted by radiant heat 

 which has passed through exterior portions of the substance 

 without melting them. 



2. In the dissolution of the ice thus effected, the substance 

 yields by the formation of liquid spaces, each possessing the 

 shape of a flower with six petals, a small vacuum being formed 

 at the centre of each flower. 



3. These flowers are generally formed in planes parallel to the 

 surface of freezing ; but some of the specimens of ice examined 

 were divided into prismatic segments by surfaces of discontinuity. 

 Each distinct segment had its own system of flowers arranged in 

 parallel planes ; but the parallelism did not extend to the flowers 

 of two distinct segments. This subject requires further investi- 

 gation. 



4. The appearance presented by masses of lake ice composed 

 of these segments, resembles that of certain specimens of glacier 

 ice in w^hich the air- and water-cavities are flattened in differ- 

 ent planes. Hence the explanation of the latter, which refers 

 them to actions peculiar to the glacier, must be received with 

 caution. 



5. The explanation hitherto given of the water associated with 

 the air-bubbles in glacier ice is untenable. In this paper the 

 phfenomenon is explained in accordance with the dynamical 

 theory of heat. It is sought to be shown that, owing to the 

 mutual action of the ice-molecules, a quantity of heat which has 

 been conducted through the substance without prejudice to its 

 solidity may liberate the molecules which bound an internal 

 cavity, and thus produce water-cells in association with the 

 bubbles of air. 



6. The converse of this takes place where two moist surfaces 

 of ice at 32° F. are brought into contact. Superticial portions 

 are thus virtually rendered central ; liquefaction is checked, the 

 film of moisture on the surfaces in contact congeals, and the 

 pieces of ice freeze together. To this process the term recjelatiun 

 has been applied. 



7. By the application of pressure, parallel surfaces of discon- 

 tinuity arc formed in lake and river ice perpendicular to the di- 

 rections in which the pressure is exerted ; thus giving the sub- 

 stance the appearance of seleuite, in which the planes of cleavage 

 are not in optical contact. The discontinuity consists in the 

 liquefaction of the ice in these planes by the pressure. Such 

 surfaces arc formed with great facility parallel to the planes in 

 which the licjuid flowers are formed by radiant heat, while it is 

 very diflicult to produce them perpendicular to these ])lancs. 



PhiL May. S. 4. Vol. 16. No. 108. Nov. 1858. 2 A 



