62 Royal Society. 



p. 81,) which the author seems to have glanced at but not 

 read. In that paper 1 stated that *' the attraction of an elec- 

 tro-magnet for pieces of soft iron at a distance was much less 

 than that of a permanent magnet of equal lifting power. This 

 peculiar property rendered the electro-magnet not well suited 

 for magnetic induction at a distance; and hence after a few 

 unsuccessful trials to substitute it for the permanent magnet in 

 my apparatus for continued rotation, it was long since aban- 

 doned." It was abandoned for this reason, not because it failed 

 in producing rotation, but simply because it did not do it so 

 well as a permanent magnet. The author in question gives the 

 following version of my statement : " Dr. Ritchie says that the 

 use of the electro-magnet in the apparatus for continued rota- 

 tion was long since abandoned, because it was incapable of in- 

 ducing magnetism in an iron bar at a distance." It is painful to 

 be forced to notice papers of this kind with which the journals 

 are constantly filled. It may appear to some that my asser- 

 tions are too broad. I appeal for the truth of them to every 

 person acquainted with the present state of the science. 



XVI. Proceedings of hearned Societies, 



ROYAL SOCIETY. 



[Continued from vol. ix. p. 537-] 



June 16. 12. " A Comparison of the late Imperial Standard Troy 

 {Continued.) -^^ Pound Weight with a Platina copy of the 

 same, and with other Standards of authority." Communicated by 

 Professor Schumacher, in a Letter to Francis Daily, 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 j which was 

 accordingly done. It was made of brass by Bate j 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. The re- 

 sult 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 

 jof the Clerk of the House of Coujmons. 



