247 



that the phenomenon is independent of diffusion. The colloidal 

 septum is capable of hydrating itself to a higher degree in contact 

 with pure water than in contact with alkaline solution. Colloidal 

 septa, swollen in consequence of contact with dilute acid or alkali, 

 appear to acquire increased sensibility to osmose, in consequence of 

 their unusually high degree of hydration. 



III. " On some new Phenomena of Residuary Charge, and the 

 Law of Exploding Distance of Electrical Accumulation on 

 Coated Glass." By Sir W. SNOW HARRIS, F.R.S. Re- 

 ceived May 17, 1861. 



(Abstract.) 



A main object of this paper is to prove that residuary charge in the 

 Leyden jar, subsequent to explosive discharge through an external 

 interrupted circuit, as in the case of discharge by a Lane's electro- 

 meter, is not the result of a spreading of the charge upon the un- 

 coated part of the glass, or of penetration within its substance, but 

 arises from an undischarged portion of the accumulation left as it 

 were behind, and still existing in precisely the same way and under 

 the same conditions as the original charge. 



The author introduces his subject with sundry observations on 

 Lane's discharging electrometer, and the law of explosive discharge, 

 and adverts to the fact recorded by Nicholson in the Royal Society's 

 Transactions for 1 789, that " although in moderate charges the ex- 

 ploding distance appears exactly, or very nearly, proportionate to the 

 charge itself, yet for high intensity, the distance to which the charge 

 is carried exceeds that proportion : " this the author finds to be the 

 case generally, and quotes an experimental example showing the 

 amount of deviation from Lane's law in that particular instance. 

 He further shows, that in order to obtain explosive discharges at the 

 increased distances agreeing with the calculated number of measures, 

 the distances must be slightly increased by certain small quantities. 



The probable sources of these differences are now adverted to, and 

 the common objections to Lane's discharging electrometer con- 

 sidered. A new and improved form of this instrument is figured and 

 described. One of its principal advantages is a means of changing 

 the exploding points of the discharging balls, which are moveable on 



