A HISTORY OF SCIENCE 



erality of mankind. In the one case as in the other, 

 any attempt to answer it to-day must partake largely 

 of the nature of a guess, yet certain forecasts may be 

 made with reasonable probability. Thus it can hardly 

 be doubted that at the absolute zero all matter will 

 have the form which we term solid; and, moreover, a 

 degree of solidity, of tenacity and compactness greater 

 than ever otherwise attained. All chemical activity 

 will presumably have ceased, and any existing com- 

 pound will retain unaltered its chemical composition 

 so long as absolute zero pertains; though in many, if 

 not in all cases, the tangible properties of the sub- 

 stance its color, for example, and perhaps its crys- 

 talline texture will be so altered as to be no longer 

 recognizable by ordinary standards, any more than 

 one would ordinarily recognize a mass of snowlike 

 crystals as air. 



It has, indeed, been suggested that at absolute zero 

 all matter may take the form of an impalpable powder, 

 the forces of cohesion being destroyed with the vibra- 

 tions of heat. But experiment seems to give no war- 

 rant to this forecast, since cohesion seems to increase 

 exactly in proportion to the decrease of the heat- 

 vibrations. The solidity of the meteorites which come 

 to the earth out of the depths of space, where some- 

 thing approaching the zero temperature is supposed 

 to prevail, also contradicts this assumption. Still less 

 warrant is there for a visionary forecast at one time 

 entertained that at absolute zero matter will utterly 

 disappear. This idea was suggested by the observa- 

 tion, which first gave a clew to the existence of the ab- 

 solute zero, that a gas at ordinary temperatures and 



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