Assumptions required for the Proof of Avogadro's Law. 433 



T=The absolute temperature of the oil-bath. 



H = Observed barometric height at the time of 



sealing. 



H' = The barometric pressure at the time of opening, 



corrected for pressure of vapour of water, at the 



temperature of the water used in filling the tube. 



Then we have 



H 7 w 2 — w\ 273 + t 

 x 



H iv 2 " T 



7 



Bio 2 (273 + 



H.'(ic 2 — W\ ) 

 In these experiments the observed values were, after making 

 all corrections, 



H = 752-4 millim. 

 H'= 744-8 „ 

 ic 2 = 5-310 grammes. 

 w x — 2*278 ,, 

 * = 15°C. 

 Hence 752-4 x 5'31 x 288__ nQ 



1_ 744-8x3-032 ~^' 



And the temperature of the oil was therefore 509 — 273 = 

 236° C. 



L. The Assumptions required for the Proof of Avogadro's 

 Law. By Professor Tait*. 



TWO months ago (in consequence of a chance hint in 

 i Nature ') I managed to procure a copy of Prof. Boltz- 

 mann's paper (ante, p. 305), and inserted a reply to it in the 

 (forthcoming) Part II. of my investigations ; but, as there 

 may be some delay in the publication, I send a short abstract 

 to the Philosophical Magazine. 



Prof, Boltzmann says that I do not expressly state that my 

 w r ork applies only to hard spheres. This is an absolutely 

 unwarrantable charge, as I have taken most especial care 

 throughout to make this very point clear. 



Prof. Boltzmann, while objecting to my remark about 

 "playing with symbols/'' has unwittingly furnished a very 

 striking illustration of its aptness. His paper bristles through- 

 out with formulae, not one of which has the slightest direct 

 bearing on the special question he has raised ! 



He asserts that, in seeking a proof of Clerk-Maxwell's 

 Theorem, I have made more assumptions than are necessary. 

 To establish this, he proceeds to show that the Theorem can 

 * Communicated by the Author. 



Phil. Mag. S. 5. Vol. 23. No. 144. May 1887. 2 G 



