-1859] WRITINGS OP JOSEPH HENRY. 97 



ment, which is frequently given in elementary books as a 

 measure of the feeble attraction of water for itself, is im- 

 properly interpreted. It merely indicates the force of attrac- 

 tion of a single film of atoms around the perpendicular 

 surface, and not of the whole column elevated. The differ- 

 ence then of liquidity and solidity principally consists in 

 the mobility of the atoms. 



The immobilit}' of the atoms of solids probably depends 

 on their being assembled in larger groups, forming crystals, 

 tissues, fibres, &c., and when force is applied to separate 

 them they all resist together. In breaking a piece of steel 

 for instance by extension, all the parts throughout the cross 

 section of the mass simultaneously resist separation, and 

 hence the great tenacity and rigidity of this substance: and 

 between this and pure water other substances may be found 

 having intermediate consistencies. 



We have said that the atoms of the setherial medium per- 

 Tade those of all other bodies, and this postulate is ana- 

 logous to the inter-penetration of the particles of different 

 substances between each other. 



If a piece of copper plated with silver be heated to redness 

 the latter metal will be absorbed into the former. Water 

 absorbs a large portion of air, and between the atoms of the 

 air itself there may exist an indefinite number of other gases. 

 Melted silver poured into water gives out a large portion of 

 oxygen, which it had previously absorbed from the air in 

 its liquid state. 



If we suj)pose solid bodies to be composed of a series of 

 groups of atoms, the larger in succession formed from the 

 smaller, the vacuity in all cases may far exceed the solidity. 



Let us now consider more minutely the nature of the 

 emanations from the sun, (light, heat, &c.,) in connection 

 with the doctrine of atoms. And in order to this we shall 

 make comparisons between the phenomena of light and 

 heat, and those of sound, passing by analogy from the pal- 

 pable and well-known cause of familiar phenomena to that 

 which is apparently not as readily accessible to our inves- 

 tigations, but which when properly understood is equally 



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