184 Scientific Intelligence.^'^Meteorology. 



does him great injury in a commercial point of view. The copper- 

 sheathing of vessels is rapidly destroyed. Mr Daniell exhibited a sheet 

 taken from the Bonetta in August 1840, on her return from the 

 African station. Although new not many months before, it was eaten 

 into holes, with a deposit on the one side of the protochloride of copper, 

 and of the black sulphuret of copper on the other. A plate exhibited, 

 taken from the Royal George, was in a good state in comparison with 

 it. T!ie latter had been acted on for sixty years by sea-water, but, 

 be it remembered, by sea- water alone, not impregnated with sulphu- 

 retted hydrogen. On it there was no trace of a sulphuret. These, 

 then, were the two principal and important points illustrated by Mr 

 Daniell ; and the question put by him, and answered in the affirmative, 

 was. Can science indicate a remedy for these evils ? For the former, 

 fumigation with chlorine. Chlorine and sulphuretted hydrogen cannot 

 co-exist. Chemical action instantly takes place; siilphur is thrown 

 down, hydrochloric acid formed, and malaria and miasma nowhere ; 

 the destroyer destroyed. For the latter, the destructive agent is not 

 decomposed, but its action is directed to a less costly material. Copper 

 is to be protected by zinc, for which sulphuretted hydrogen has the 

 stronger affinity ; and so long as the latter metal is present, the former 

 is free from the attack of the gas in solution. This, it will be readily 

 seen, is Sir H. Davy's principle, which involved the use of zinc or iron ; 

 but in the case of sulphuretted hydrogen, zinc and not iron must be 

 employed. Mr Daniell regretted that Davy's zinc-protectors had been 

 so soon abandoned, and only because the copper, not acted upon by the 

 muriatic acid, became a nucleus for earthy, vegetable, and animal 

 matter, and the ship's bottom was in consequence fouled, as it is 

 termed. The remedy for this, he said, was most simple. Let the 

 protectors be so arranged that contact may be broken and renewed at 

 will. The zincs and copper separated for a short time, the earthy de- 

 posits would soon be removed. In consequence of Mr Daniell's report 

 to the Admiralty, chlorine has been furnished the Niger Expedition, 

 and no ship hereafter will proceed to the African station without that 

 purifier in store, nor without zinc-protectors for her copper. It is to be 

 hoped that all ship-owners will follow the example of the Admiralty 

 Board in this respect. — Literary Gazette, No. 1272. 



AikUtional Evidence of the active agency of Salt Water ^ when in contact with 

 decaying Vegetable Mattery in Generating Miasma, in a hot climate, con- 

 tained in a Letter from Professor Daniell to the Editor of " The Friend (f 

 Africa:' 



My DfiAR Slft,'-*Tho fividcncc of the worsit ea^^es of malaria beiu^ C9it< 



