1820.] Phyiical Science during the Year 1819. 17 



adopting a more complicated number. Nature delights iu sim- 

 plicity. Hence I am led to expect simple numbers for the 

 weight of the atoms of the simple bodies. 



9. Cadmium. — I have nothing to add to the account of this 

 metal which I gave in last year's historical sketch, except to 

 refer the reader to a paper drawn up by Prof. Gilbert, a translation 

 of which I inserted in the Annals of Philosophy, xiv. 269. It 

 contains all the characters of this new metal detailed by Stro- 

 meyer in his different papers on the subject, and must be of 

 considerable utility to all those who undertake the examination 

 of the zinc ores which contain cadmium. 



The reader is aware of the interesting discovery by Dr. 

 Clarke of cadmium in a silicate of zinc from Derbyshire, an 

 account of which will be found in the Annals of Philosophy, xv. 

 272. I may mention that I have lately had an opportuuity of 

 examining a carbonate of zinc from Derbyshire, which was of a 

 dirty white colour, with red spots here and there, which I found 

 contained almost exactly half a per cent, of cadmium. 1 extracted 

 the metal by the process of Stromeyer, and took the opportunity 

 of subjecting the new metal to a few trials in order to make 

 myself acquainted with the appearances which it exhibits when 

 treated with various reagents. It is probable, I think, from 

 these two examples of cadmium occurring in two different 

 British ores of zinc that British chemists will soon have it in 

 their power to obtain this new metal at least in quantities suffi- 

 cient to subject it to a correct examination. 



10. Bismuth. — The analogy between bismuth and lead is well 

 known to chemists. The two metals resemble each other like- 

 wise in their volatility. It appears from the experiments of 

 Chaudet, that bismuth is volatilized if it be kept in the tempera- 

 ture of 30° Wedgewood,even though it be covered with a coar- 

 ing of charcoal. {Annals of Philosophi/, xiv. 229.) 



11. Mercury. — Mr. Donovan's experiments to determine the 

 composition of the oxides and salts of mercury, to which I alluded 

 in the historical sketch of last year, have been since pubhshed 

 in the Annals of Philosophy, xiv. 241. Every chemical reader 

 who peruses the paper will agree with me in thinking that it 

 possesses unquestionable merit, and that Mr. Donovan has 

 added veiy materially to the accuracy of our knowledge of the 

 combinations of mercury. For my own part at least I can safely 

 say that I derived a great deal of additional knowledge from the 

 perusal of Mr. Donovan's paper, and that I should have regret- 

 ted exceedingly had it remained unpublished. 



Mr. Donovan finds that the best way of procuring protoxide 

 of mercury is to mix calomel at once with a considerable quan- 

 tity of caustic potash, and triturate them together. When the 

 globules of running mercury are separated, a black powder 

 remains, which is protoxide of mercury. He finds the composi- 

 tion of the two oxides of mercury as follows : 



Vol XVI. N° I. B 



