Page:A voyage round the world, in His Britannic Majesty's sloop, Resolution, commanded by Capt. James Cook, during the years 1772, 3, 4, and 5 (IA b30413849 0001).pdf/61

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vered with mould, and all our iron and steel though ever so little exposed, began to rust. Nothing is more probable than that the vapours, which now filled the air, contained some saline particles, since moisture alone does not appear to produce such an effect. If it be asked how any saline particles, generally so much heavier than the aqueous, can be raised in vapours, I leave it to the philosophers to determine, whether the numerous animal parts which daily putrefy in the ocean, do not supply enough of the volatile alkali, by the assistance of which the above phænomenon might be explained. The great heat between the tropics seems to volatilise the marine acid contained in the brine and common salt: for it has been observed, that on rags dipped in a solution of any one of the alkalies, and suspended over one of the pans where brine is evaporated and salt is prepared, crystals are soon formed of a neutral salt, compounded of the marine acid and the alkali in which the rags had been immersed; hence perhaps we may be allowed to infer, that the marine acid is by the heat of the tropical sun volatilised, and in that aërial or vaporous form attacks the surface of iron and steel; nay, this little quantity of acid may perhaps, imbibed by the lungs, and pores of the skin, become salutary; in the first case to people under pulmonary diseases;

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