448 Lord Rayleigh. On the [Mar. 27, 



VIII. The accessory ossicles developed in its vicinity, which are 

 six. One, a detached portion of the lachrymal itself, with a second 

 ossific centre (ossiculum hamuli) ; one, a detached portion of the 

 os planum behind it (ossiculum ethmo-lachrymale superius) ; two, 

 which are detached nodules connected with the maxilla (ossiculum 

 ethmo-lachrymale inferius and ossiculum canalis naso-lachrymale) ; 

 one, which belongs to tie system of the jugal bone (ossiculum infra- 

 orbitale) ; and one, a detachment of the nasal process of the maxilla 

 (ossiculum maxillo-frontale). To this last-named the sutura notha 

 is always related. 



IX. The history of the development of the human lachrymal from 

 its first appearance in the eighth week, and the changes in position 

 and slope shown by it. 



X. The racial varieties shown by this bone, and the system of inter- 

 lachrymal indexes whereby the degree of downward divergence and 

 orbital splay of the bone can be measured. 



XI. Comparative anatomy and morphology of the bone. Those 

 points have been briefly referred to which help to interpret the human 

 conditions. 



II. " On the Electro-Chemical Equivalent of Silver, and on the 

 Absolute Electromotive Force of Clark Cells." By Lord 

 Rayleigh, D.C.L., F.R.S. Received March 17, 1884. 



(Preliminary Notice.) 



The investigations upon this subject which have been carried on by 

 Mrs. Sidgwick and myself during the last year and a half, though 

 not yet quite finished, are so far advanced that no doubt remains as 

 to the general character of the results ; and as these results have 

 application in the daily work of practical electricians, it is thought 

 desirable to communicate them without further delay. 



The currents are measured by balancing the attraction and repul- 

 sion of coaxal coils against known weights, as described before the 

 British Association in 1882, a method which has fully answered the 

 favourable expectations then expressed. To what was said on that 

 occasion it will be sufficient for the present to add that the readings 

 are taken by reversal of the current in the fixed coils, and the 

 difference of weights thus found (about 1 gram) represents the 

 double force of attraction, free from errors depending upon the con- 

 nections of the suspended coil, and other sources of disturbance. 



The difficulties which have been experienced, and which have been 

 the cause of so much delay, have related entirely to the behaviour of 

 the silver voltameters, of which never less than two, and sometimes 



