Mr. Whelpley on the Idea of an Atom. 361 



C 0' 

 If in any two atoms of the same kind, p w, p' W, 



acting from a distance, p n is shorter than p'n', it is of a different 



temperature, but of the same gravity, the intensity p n, being 



greater as the diameter pn is less. The gravity of the two atoms 



will,' therefore, be unaffected by their differences of bulk, (i. e. of 



temperature.) 



There must be a temperature at which an atom ceases to ra- 

 diate, or attains its normal bulk, than which it may be either 

 less or greater, and toward which it constantly tends. This 

 temperature is the normal dimension of the nucleus, relatively to 

 that of all other nuclei. If C therefore be less than its normal 

 bulk it will expand, radiating " cold pulses." The relation of 

 C to C is such, that as soon as this difference in the one atom 

 is felt at the nucleus of the other, a compensatory change must 

 happen in this latter; as in the instance of contact. The radi- 

 ant pulse is " absorbed" by the nucleus ; which thereupon con- 

 tracts ] or, if the radiation be a " heat pulse," it expands. . 



But the phenomena of radiation require a minuter examination 

 than would be consistent with the purpose of this article; which 

 is to show the possibility, only, of the idea of an universal atom, 

 that shall serve as a basis for calculation. 



Since a smaller atom should move and change its temperature 

 by shorter pulses, and the red rays are known to be the shortest 

 visible rays, the nuclei of all atoms at a red heat should be of 

 one and the same diameter. Gases and liquids, being for the 

 most part blue, should originate longer and feebler pulses, be- 

 cause the nuclei of their atoms are larger. Facts like these sug- 

 gest the possibility of finding the dimensions of the atoms ; for 

 we know already the lengths of the pulses of light, and the nu- 

 clei must be larger than the pulses they excite. 



The three conditions, liquidity, solidity and aeriformity. 



The theory of comets, and of planetary atmospheres, rests upon 

 the hypothesis of a mutual gravitation of gases. Let it be as- 

 sumed that the nuclei of two atoms of gas floating free in space 

 will approach each other, until, at a certain limit, their attraction 

 is converted into repulsion. This limit will determine the size 

 of their repellent nuclei.* Change of temperature being only a 



* " Atmospheres of repulsion," if the word atmos is taken to mean pure force, 

 as if from the Sanscrit atma. 



