196 Mr, Bfayk^ on the Rationale of the Formation [Sept. 



chemistry ; and then proceed to adduce experimental evidence 

 that it actually occurs in some cases, distinguished from other* 

 only by the circumstance of their taking place at temperatures 

 sufficiently low, to allow of their being made subjects of experi- 

 mental observation. 



It will be sufficient merely to state that Mr. Faraday's experi- 

 ments on the liquefaction of gases,* have annihilated the 

 distinction formerly believed to exist between gases and vapours^ 

 and have shown them to differ merely in density, and conse- 

 quently that the passage from the rarest gas to the densest, 

 vapour is by indefinable and continuous degrees. In like 

 manner, the experiments of M. Cagniard de la Tour on the 

 combined action of heat and pressure on certain liquids,t toge- 

 ther with some now well-known facts indicated by the phaeno- 

 niena attending the production of steam from the generator of 

 Mr. Perkins^s steam-engine, show, I think, that no line of 

 demarcation can be drawn between vapours and liquids, but that 

 they likewise pass into each other in a perfectly continuous 

 jnanner, by imperceptible degrees. It appears to me, in short, 

 that the aggregate of our knowledge respecting the different 

 forms of ponderable matter, as regards their relations to latent 

 heat, according to the received doctrine on the cause of fluidity, 

 leads directly to the conclusion, that there are only two such 

 forms, the solid and the Ji aid; the distinction of the latter into 

 atriform and liquid being still however retainable with propriety 

 as a matter of convenience, though there seems every reason to 

 believe it a distinction that has no real existence. The accurate 

 reasoning of Mr. Graham, I may also remark, in his observations 

 on the absorption of gases by hquids, quoted in the same number 

 of the Annals in which Dr. Colquhoun's paper appears, as well 

 as the experimental evidence he cites, is entirely favourable to 

 this view of solidity and fluidity being the only distinct physical 

 forms, or states of aggregation, of ponderable matter; the 

 gsLseous and the liquid states being merely continuous degrees of 

 one and the same form .if 



♦ See Phil. Trans, for 18S3 ; orJnnalsy N. S. vol. vii. p. 89. 



+ Ann. do Chim. et de Phys. torn. xxi. ; or Annals^ N. S. vol. v. p. 290, 



t Since the above paragraph was written, I have read a paper by Professor Oersted, 

 published in Schweigger's Journal for December last, in which are detailed the results 

 of a series of experiments made by him and Capt. Schwendsen, with the view of deter- 

 mining whether the law of the compression of aeriform bodies discovered by Mariotte 

 extended to high pressures, which had been doubted by certain mathematicians. The 

 result was the coniplcte verification of 31 ariottc's law for all j)ressures, whilst the gases 

 retain their aeriform state. At the conclusion of the paper, l*rof. Oersted expresses his 

 opinion, derived from experiment, that liquids are subject to the same law ; and if this 

 shall, on furtlier investigation, prove to be the fact, it will tend to confirm my opinion, 

 given above, that the gaseous and the liquid states "are essentially the same. 



The following is a translation of the pa.ssage: — *' The compression of liquid bodies 

 reducible to drops, is, as far a.s our experience yet goes, subject to the same law ; here, 

 too, the compression and tlie compressing power seem to bear a direct relative propor- 

 tion. AVc may, therefore, assume, that the gases, converted into liquids reducible to 

 drops, begin again to follow the same law to which they answered as gases. If this 

 should be confirmed l)y further expcrimejits, it may l)c said that the compression of 



