SOLIDS, LIQUIDS, AND OASES. 371 



ing; a theory which assumes that the pressure first thaws a 

 film of ice at the surface of contact, and that presently this 

 re-freezes, and thus effects a healing or general solidifica- 

 tion. Faraday found that two pieces of ice with moistened 

 surfaces united if pressed together when at just about the 

 temperature of freezing, but not if much colder. Tyndall 

 has further illustrated this by taking fragments of ice and 

 squeezing them in a mould, whereby they became a clear, 

 transparent ball, or cake. Schoolboys did the like long be- 

 fore, when snowballing with snow at about the thawing 

 point. Such snow, as we all remember, became converted 

 into stony lumps when firmly pressed together. We also 

 remember that in much colder weather no such cohesion 

 occurred, but our snowballs remained powdery in spite of 

 all our squeezing. 



I am a sceptic as regards this theory of regelation. I 

 believe that the true explanation is much simpler; that the 

 crystals of snow or fragments of ice in these experiments are 

 simply welded, as the smith unites two pieces of iron, by 

 merely pressing them together when they are near their 

 melting point. Other metals and other fusible substances 

 may be similarly welded, provided they soften or become 

 sufficiently viscous before fusing. 



Platinum is a good example of this. It is infusible in or- 

 dinary furnaces, but becomes pasty before melting, and. 

 therefore, one method adopted in the manufactore of plati- 

 num ingots or bars from the ore, is to precipitate a sort of 

 platinum snow (spongy platinum) from its solution in acid, 

 and then compress this metallic snow in red-hot steel 

 moulds by means of pistons driven with great force. The 

 flocculent metal thus becomes a solid, coherent mass, just 

 as the flocculent ice became coherent ice in Tyndall's experi- 

 ment or in making hard snowballs. 



"Wax, pitch, resin, and all other solid sthat fuse gradually, 

 cohere, are weldable, or, in very plain language, "stick 

 together/' when near their fusing point. 



I have made the following experiment to prove that 

 when this so-called regelation of snow or ice-fragments 

 occurs, the ice is viscous or plastic, like wax or pitch. A 

 strong iron squirt, with a cylindrical bore of half an inch 



