409 



gas, differing in equivalent combinations, according to the peculiar 

 constitution of the plant; and thus the foundation is laid for all that 

 prodigious diversity which characterizes the numberless species of the 

 vegetable creation. 



12. " A Comparison of the late Imperial Standard Troy Pound 

 Weight with a Platina copy of the same, and with other Standards 

 of authority.' , Communicated by Professor Schumacher, in a 

 Letter to Francis Baily, Esq., V.P. and Treas. of the Society. 



Professor Schumacher being desirous of procuring an accurate 

 copy of the English Imperial Standard Troy pound weight, for the 

 purpose of comparison with the Danish weights, applied to Capt. 

 Kater, requesting him to cause such copy to be made , which was 

 accordingly done. It was made of brass by Bate ; but the result 

 of the weighings not being satisfactory to Professor Schumacher, 

 he desired to have a second copy forwarded to him. As these two 

 copies did not agree in their results, the first was returned to Capt. 

 Kater with a request that he would repeat the weighings. There- 

 suit confirmed Professor Schumacher's suspicions : and as it was 

 not thought proper that, in an affair of so much importance as the 

 comparison of the standard weights of two nations, any source of 

 discordance should exist, or even be suspected, (the preceding ex- 

 periments having been made with a copy of the Imperial standard 

 weight) the Danish Government sent over Capt. Nehus (of the 

 Royal Danish Engineers) to this country for the express purpose of 

 making comparisons with the original standard, in the possession 

 of the Clerk of the House of Commons. 



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 Cary, 

 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 original 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 



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