23 Sir D. Brewster on a singular Developitient of 



moistened hands, the intensity of the rapid succession of shocks 

 will be found absolutely intolerable, even when the battery 

 used consists of but two plates presenting each 6 or 8 square 

 inches of surface. 



This magnetic contact-breaker will, 1 flatter myself, be found 

 eventually of service to the chemist for electrolytic purposes ; 

 whilst as affording a ready mode of applying voltaic electricity 

 for medical purposes, I think it will be considered of con- 

 siderable service as dispensing with manual labour, and afford- 

 ing currents ot far greater intensity than can be obtained 

 from several dozen, or even a far greater number of pairs of 

 plates excited by strong acids, a process equally inconvenient 

 and expensive. 



In conclusion, I ought to observe that the application of a 

 permanent magnet to effect the rupture of contact without 

 manual labour is by no means original with me, although in 

 justice to myself 1 must state, that when I first contrived the 

 above-described instrument I was not aware of a similar prin- 

 ciple having been adopted for this purpose. In the last num- 

 ber of Prof. Silliman's Journal is a paper by Dr. Page de- 

 scribing several pieces of apparatus to be used with Dr. 

 Henry's gigantic coils ; one of these contrivances, ill-described 

 however, consists of a bar of iron covered with a helix oscil- 

 lating between the poles of a single permanent magnet, con- 

 stituting, from my own experience, a very ineffective arrange- 

 ment. To Dr. Page, however, must in justice be accorded 

 the originality of the application of permanent magnets for 

 the purpose of breaking contact. 



I remain, my dear Sir, yours truly, 

 22, Wilmington Square, Nov. 2, 1837- GoLDING BiRD. 



To Richard Phillips, Esq., F.R.S. L. ^ E., Sfc. 



N.B. The contact-breaker described in this letter was con- 

 structed for me by Mr. Neeves, of Great St. Andrew's Street, 

 Holborn. 



V. On a singular Development of Polarizing Structure in 

 the Crystalline Lens after Death ; and. on the Cause, the Pre- 

 vention, and iheCure of Cataract. By Sir David Brewster, 

 K,G,H,, V.PKS.Ed.* 

 TN examining the changes which are produced by age in 

 -■- the polarizing structure of the crystalline lenses of animals, 

 I was induced to compare these changes with those which I 



• From the Report of the Sixth Meeting of the British Association : 

 Transactions of the Sections, pp. 16, 1 1 1 . Sec Lend, and Edinb. Phil. Mag., 

 vol. viii. pp. 193, 416. 



