Imperial Standard Troy Fotmd. 63 



The weighings took place in the Apartments of this Society, and 

 were partly made with Ramsden's balance, belonging to the Society. 

 Besides the first brass weight above mentioned, there was another 

 brass weight made by Robinson, a platina weight made by Gary, 

 the brass pound weight belonging to the Royal Mint, and the 

 platina pound weight belonging to this Society. These were all 

 subjected to a most rigid and accurate series of weighings by Capt. 

 Nehus, in which every precaution was taken to insure the most 

 correct results. It would be impossible here to follow Capt. Nehus 

 through all his details : but it may be sufficient now to state that 

 upwards of 600 comparisons were made with the English Imperial 

 standard, all of which are apparently very accordant ; but, on ac- 

 count of a singular circumstance connected with the ori^/nrt/ stand- 

 ard, do not possess that degree of precision, nor afford that satis- 

 faction which ought to attach to an affair of so much importance. 

 For, it appears that not only the specific gravity of the original 

 standard had never been ascertained, but that we are even ignorant 

 of the kind of metal of which it was composed : some persons main- 

 taining that it was of brass, others of copper, and others of bell- 

 metal. And, as the original was totally destroyed in the late fire 

 which consumed the two Houses of Parliament, we cannot now 

 supply this omission. It is well known that the specific gravity of 

 brass may vary from 7*5 to 8'5 ; so that a difference of at least ^ of 

 a grain might arise from this circumstance alone ; setting aside a 

 number of other particulars that require minute attention, and 

 which do not seem to have been attended to in former experiments 

 of this kind. In fact, as Professor Schumacher remarks, though 

 we have thus five different pounds in excellent preservation, and com- 

 pared with the lost standard, with the greatest care and the best 

 instruments, though the number of these comparisons exceeds 600, 

 yet there still remains an uncertainty as to its real weight; and this 

 solely on account of its specific gravity and expansion not being 

 known. And, he adds, that it is to be hoped that no pound will in 

 future be declared a legal standard unless these elements (the know- 

 ledge of which is indispensable even for a single comparison with a 

 good balance) are previously determined with the greatest possible 

 precision. 



Besides the account of these numerous weighings, which are 

 stated in detail, Professor Schumacher has given various formulae 

 and tables which will be found of great use and application in any 

 future experiments of a like kind that may be undertaken. 



13. " On the Application of a New Principle in the Construction 

 of Voltaic Batteries, by means of which an equally powerful current 

 may be sustained for any period required j with a description of a 

 sustaining battery recently exhibited at the Royal Institution." By 

 Frederick W. Mullins, Esq., M.P., F.S.S. Communicated by 

 N. A. Vigors, Esq., F.R.S.* 



The method resorted to by the Author for obtaining a continu- 

 ous voltaic current of equal intensity, is the same in principle as 



• See Lond. and Edinb. Phil. Mag., vol. ix . pp. 121, 283. 



