62 Mr. J. S. Stuart Glenuie on the 



even when the gases in the interior are under a pressure of 7 to 

 8 centimetres of mercury. 



4. This experiment may be made more striking by the fol- 

 lowing method : — the earthen tube is enclosed in a larger glass 

 tube, and carbonic acid is passed into the annular space between 

 the two tubes, while hydrogen traverses the earthen tube. The 

 two gases emerge by two distinct delivery tubes. One of the two 

 currents of gas is inflammable, and it is precisely that which pro- 

 ceeds from the end of the apparatus communicating with the 

 source of carbonic acid. The gases change their places during 

 this short and rapid passage. 



X. On the Principles of Energetics. Part II. Molecular Me- 

 chanics. By J. S. Stuart Glennie, M.A., F.R.A.S. 

 ("Concluded from vol. xxi. p. 358.] 

 31. JTHHE misconception of my theory of material forces 

 A displayed in the remarks of Professor Challis *, seems 

 to require a brief and, I trust, clearer restatement of the pro- 

 posed first principle of Molecular Mechanics, along with its 

 second and third principles, before proceeding to their applica- 

 tion and development. 



32. (I.) Matter is conceived as made up, not of an elastic 

 sether and inelastic atoms, but of elastic molecules of different 

 orders as to size and density. 



If a rough physical conception of these molecules be required, 

 they may be conceived as sethereal nuclei, the aether of the nuclei 

 of a lower being made up of nuclei of a higher order, and so on 

 ad infinitum. 



I shall, perhaps, best defend this principle by restating the 

 experimental objections to that for which it is substituted : — (1) 

 We are led by experiment to conclude that all matter is elastic, 

 and hence we are not justified in assuming two kinds of matter, 

 an elastic and inelastic. (2) Not to speak of the inconsistency 

 of denying to the atoms the elasticity which is attributed to the 

 aether, which must be made up of atoms, it is impossible to con- 

 ceive that, from any arrangement of inelastic atoms, the elasticity 

 of the bodies they constitute should arise ; though it is at once 

 admissible that degrees of elasticity may depend on the arrange- 

 ment of elastic atoms. (3) The action of an elastic sether, or 

 anything else, on an " absolutely hard, ultimate atom " is expe- 

 rimentally inconceivable; for all known action of one body on 

 another implies motion of the particles of that other body. If 

 a body is struck, it is heated, and moves; if it moves little, it is 



* Phil. Mag. p. 504, June 1861. 



