548 Intelligence and Miscellaneous Articles. 



5. Wroblewski states that the isopyknics, on approaching the 

 vapour-pressure curve, form a bundle of curves parallel to the 

 vapour-pressure curve. We have already pointed out that facts 

 contradict this view. 



6. Wroblewski restates a view, propounded by one of us in 

 the Proc. Roy. Soc. xxx. p. 323. This view must, in consequence 

 of our more accurate and recent researches, be abandoned. The 

 distinction between liquid and gas above the critical point is wholly 

 illusory ; and we believe that such distinction would also disappear 

 below the critical point, were it possible to follow experimentally 

 the continuous change from liquid to gas. 



7. Wroblewski also asserts that heat is required to convert liquid 

 into gas at the critical temperature. We have only to refer to our 

 published papers on the thermal properties of alcohol and ether 

 (Trans. Roy. Soc. 1886, part i. plate 5, and 1887, part i. plate 5) 

 to disprove this assertion. Moreover all our experimental obser- 

 vations tend to show that no abrupt change of state occurs at any 

 point on the isothermal ; in fact that heat of vaporization vanishes, 

 its place being taken by heat due to compression or expansion. 



8. Andrews does not make the statement attributed to him by 

 Wroblewski, but gives a qualified definition of the words " liquid " 

 and "gas." 



It will thus be seen that our results contradict Wroblewski's 

 views in every particular ; and that there is no reason to reject the 

 views of Dr. Andrews as regards the liquid and gaseous states. 

 We are, Gentlemen, 



Your obedient servants, 



William Ramsay, 

 Sydney Toujstg. 



LECTURE EXPERIMENTS ON THE CONDUCTIVITY OF SOUND. 

 BY M. HESEHUS. 



Rods of the size of an ordinary pencil are prepared of steel, 

 glass, wood, guttapercha, cork, and caoutchouc. They are con- 

 nected in threes by means of a caoutchouc rod, tubes of the same 

 material being interposed between them. The rods are held in 

 one hand, with their lower ends on a sounding-box, and the free 

 ends are successively touched by the stem of a vibrating tuning- 

 fork, which is held in the other hand. The sound is not perceptible 

 when the caoutchouc rod is touched, but it becomes more so as the 

 other rods are successively touched. It can thus be shown that the 

 intensity remains constant, if one rod is replaced by another of the 

 same material, but the dimensions of which vary in the same pro- 

 portion. By varying the length alone the intensity is changed ; in 

 like manner it is changed also by varying the section while the 

 length is constant. The method is sufficiently sensitive to show 

 the difference between the conductivity of wood parallel and per- 

 pendicular to the fibres, and even to determine the numerical ratio 

 of these conductivities. — Journal de Physique, April 1887. 



