Dr. Williamson on the Dynamics of the Galvanic Battery, 353 



at the zero-point of gaseous tension, — a very significant fact in 

 molecular physics. To this central point or ether-node (as it 

 may be termed) converge the lines of the greater number of the 

 vapours experimented upon by M. Regnault. But water, alcohol, 

 and sulphuric acid hydrates are notable exceptions; and there 

 are others, viz. pyroxylic spirit, pyroxylic ether, sulphurous acid, 

 and oxalic ether, which seem to trend towards the water-node. 



The liquid-expansion lines fas those on Plate marked -=-1 of 



the same three ethers, projected from M. Pierre's observations 

 of expansion, give the following values for Gr, the upper limiting 

 temperature reckoned from the zero of gaseous tension (or 

 G=274 + ry), and the molecular volumes at the same zero 



V.D. 



/*= , or quotient of the vapour-density of the ether by its 



specific gravity at —274°, computed by means of the equation 

 {log 7 -log( 7+ 274)}^=(t,-l). 



'} 



(1) 460-0 26-0 3-22 55^3 



(2) 534-4 27-8 3-32 57*9 )» Mean 56-5, 



(3) 597-4 31-1 3-41 56-3 



It will be remarked that the numbers in columns G and fx are 

 nearly proportional to those above in columns h and g. The 

 same equality of ratio is found in other cases. 



There are also certain apparent relations of harmony in the 

 absolute measure of liquid cohesion of a molecule as deduced 

 from the latent heat of its vapour. Thus the latent heat of a 

 molecule of water is exactly the same as that of a molecule of 

 alcohol at 0°. 



The latent heat of a molecule of hydrochloric ether is to that 

 of hydriodic ether as the initial molecular volumes at —274° ? 



Edinburgh, March 16, 1864. 



LVII. On the Dynamics of the Galvanic Battery, 

 By Dr. A. W. Williamson, F.R.S. 



To Dr, Francis ', F.L.S. §•<?. 

 Dear Sir, 



IT appears to be incumbent on me to say a few words in reply 

 to Mr. James Napier's letter in a recent Number of the 

 Philosophical Magazine, impugning some statements which I 

 Phil. Mag. S. 4. Vol. 27. No. 183. May 1864. 2 A 



