Electrical Discharge. 351 



that the construction of my instrument is imperfect*, and " that 

 is the reason why my experiments have been unfruitful," more 

 especially when we see that almost every experimental deduction 

 arrived at by M. Riess, by means of what he considers a better 

 construction, is in perfect accordance with results I had already 

 obtained. I trust I have clearly shown (10) that the solitaiy 



Q2 



exception taken by M. Riess in his expression Ta — is, after all, 

 no exception at all ; the expression being, in fact, no other than 



Q2 



my own formula Ta — previously deduced, since the symbols s 



and r may be taken to represent the same thing, viz. resistance 

 to discharge. 



17. Since the diflference in question bears upon a large and 

 important class of physical researches, I am unwilling to leave 

 the subject without some few additional observations. My first 

 experiments, given in the volume of the Plymouth Institution 

 before mentioned (1), contain illustrations of the diminished 

 heating effect of a given quantity of electricity when accumulated 

 on, and discharged from, many jars — the only point, in fact, 

 upon which M. Riess founds his objection to ray instrument in 

 the way I consti-ucted it. It will be found at page 16 of this 

 paper, that the quantity of electricity was measured in precisely 

 the same way as that subsequently adopted by M. Riess, many 

 years after, that is, by the explosions of a Lane's jar in commu- 

 nication with the insulated negative side of the battery, although 

 M. Riess, full seven years after (Poggendoi'ff's Annalen, vol. xl. 

 p. 324), claims for himself the especial merit of having first 

 applied this practically. If M. Riess, however, will favour me by 

 a perusal of my memoir above referred to (1), he will find the 

 whole arrangement exactly as he describes it, fully detailed and 

 figured, p. 63, fig. 16, printed in 1830. The method, how- 

 ever, which I finally adopted to measure the quantity of elec- 

 tricity in the battery, as being the most accurate and convenient, 

 was the interposition of a small Leyden phial between the con- 

 ductor of the machine and the battery, and which I have termed 

 a " unit jar " or measure. It is fully described in the Philoso- 

 phical Transactions for 1834't. The electric jars first subjected 

 to experiment wei-e part of a battery originally constructed by 

 Cuthbertson, each jar being 18 inches high and 4 inches in dia- 



* " It is probably to the imperfection of the one (thermo-eleetrometer) 

 emjiloyed by -Mr. Harris that we must attribute the inaccuracy of his cou- 

 chisions." — l)e hi Hive, vol. ii. p. 21.5. English translation. 



t Page 217- Nothing can exceed the accuracy of this measure, although 

 M. Kiess labours to show the eoutrary. 



