Mr. J. E. Myers on a new Volumenometer . 195 



On the contrary, the tendency of investigation has been 

 rather the other way ; for the most recent conclusions of 

 Helmholtz himself have tended to confirm Hering's views as 

 to the large predominance of the white element in the 

 spectral colours, and to establish almost exactly two of his 

 fundamental colour-sensations. 



Athenaeum Club, S.W, 

 June 1893. 



XVIII. On a new Volumenometer. 

 By J. E. Myers, B.Sc* 



THE instrument described below was devised by Professor 

 Stroud some three years ago, with the view of having a 

 volumenometer which should be capable of yielding more 

 accurate results than could be obtained by the older methods. 

 After the instrument was made some preliminary trials 

 showed that considerable difficulties would be encountered 

 in making the instrument air-tight, and in consequence of 

 the pressure of other work the instrument was put on one 

 side till last October, when it was placed in my hands. 



Various instruments, the principle of whose action is based 

 on Boyle's law, have been devised with the object of deter- 

 mining the volumes of bodies without immersing them in 

 liquids. The ordinary volumenometer devised by Say is 

 described in textbooks, but a little calculation shows that no 

 great accuracy can be obtained by its use. In BiidorfFs 

 volumenometer! determinations are made by running out 

 mercury from the cavity of the instrument, thereby increasing 

 the volume until the pressure is reduced to a certain fixed 

 value. After the body has been placed in the cavity of the 

 instrument a precisely similar experiment is performed. From 

 a knowledge of the weights of mercury which run out in the 

 two cases, the volume of the body introduced follows by 

 a simple calculation. In Paalzow's volumenometer \ mea- 

 surements are made by increasing the volume of the instru- 

 ment to a certain fixed limit, first without and then with the 

 body in the cavity. The pressure, recorded by the mano- 

 meter attached, is noticed in each case, whence the volume 

 required is calculated. Baumhauer's volumenometer § differs 



* Communicated by the Physical Society : read June 23, 1893. 



t Wied. Ann. vi. p. 288. 



% Ibid. xiii. p. 332. 



§ Archives Nierlandaises, 



