188 F. W. Very— A Cosmic Cycle. 



The very definition of an element is provisional and con- 

 fesses " intellectual impotence." Admitting the unsatisfactory 

 nature of the foundations of chemical knowledge, "it is impor- 

 tant to keep before men's minds the idea of the genesis of 

 the elements ; this gives some form to our conceptions, and 

 accustoms the mind to look for some physical production of 

 atoms. It is still more important to keep in view the great 

 probability that there exist in nature laboratories where atoms 

 are formed and laboratories where atoms cease to be."* 



Heat and pressure favor the dissolution of certain chemical 

 compounds, or the transformation of complex and unstable 

 forms into simpler ones. The common mode of preparing pure 

 metals is by the action of heat on complex mixtures of com- 

 pounds. Chloride of nitrogen breaks up into its component 

 elements with explosive violence by simple percussion. All 

 compounds have temperatures of dissociation, more or less 

 high, at which they are completely resolved into their elements. 

 If w T e have hitherto failed to decompose the elements, we may 

 infer that it is because the pressures or temperatures at our 

 command have not been great enough. 



Pressure, and not heat, is to be invoked as the prime factor 

 in atomic dissolution. The process is not reversed by any fall 

 of temperature, and therefore is unlike the dissociation of 

 chemical compounds by heat. The present suggestion differs 

 from those of Hunt and Clarke, which foresaw only an exten- 

 sion of processes already known. Lockyer also has predicated 

 heat as the cause of atomic dissolution, whereas in the present 

 view it is its consequence. 



An objection to the hypothesis of elemental destruction may 

 be urged, since, while it is conceivable that the elements may 

 be decomposed by great pressure and intense heat, there is no 

 permanent process in nature which does not move in cycles. 

 If atoms can be destroyed, how and where are they reproduced ? 

 Without such reproduction the resolution of the material 

 universe into one or more forms of matter of small atomic 

 weight would be more probable than its actual wonderful 

 diversity and the considerable atomic weight of its leading 

 constituents. 



As to the history of material substances in their purest or 

 atomic forms, there are only two alternatives. Either the 

 atoms are eternal and unchangeable, in which case suns may 

 grow cold and disintegrate, and new systems may be built of 

 their fragments at remote intervals,+ permitting a kind of 



* Loc. cit , p. 560. 



f'Two bodies, each one-half the mass of the sun. moving directly towards 

 each other with a velocity of 4*76 miles per second, would by their concussion 

 generate in a single moment 50,000,000 years' heat," says Croll in his paper on 

 the •' Probable Origin and Age of the Sun" (Quarterly Journal of Science, July, 

 1877), quoted in the " Autobiographical Sketch of James Croll, with Memoir of his 



