EVOLUTION OP SULPHURETTED HYDROGEN. 255 
as in Essex, that where the sea has been prevented flooding 
the mashes, that locality, previously very sickly, had be- 
come perfectly salubrious. To sulphuretted hydrogen, there- 
fore, Mr. Daniell ascribes the dreaded malaria, as also the 
deadly stinking miasma of Africa, producing languor, nausea, 
disgust, and death. The jungle-fever of India, also, he thinks 
attributable to its presence. The soil abounds with sulphates 
of magnesia and soda ; must not, therefore, quantities of sul- 
phuretted hydrogen be generated in the jungle-swamps? Be- 
sides the direful consequences to the health of man visiting 
the deadly shores of Africa, this sulphuretted hydrogen does 
him great injury in a commercial point of view. The cop- 
per-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 compari- 
son with it. The latter had been acted on for sixty years by 
sea-water, but, be it remembered, by sea-water alone, not im- 
pregnated with sulphuretted 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 sulphuret- 
ted hydrogen cannot co-exist. Chemical action instantly 
takes place ; sulphur is thrown down, hydrochloric acid 
formed, and malaria and miasma nowhere ; the destroyer de- 
stroyed. For the latter, the destructive agent is not decom- 
posed, 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 
