212 HISTORY OF 



scincely any substance is found capable of resisting the corrod- 

 ing qualities of the air. The air. say the chemists, is a chaos 

 furnished with all kinds of salts and menstruums ; and, there- 

 fore, it is cajmble of dissolving all kinds of bodies. It is well 

 known, that copper and iron are quickly covered, and eaten with 

 rust , and that, in the climates near the equator, no art can keep 

 them clean. In those dreary countries, the instruments, knives, 

 and keys, that are kept in the pocket, are nevertheless quickly 

 incrusted ; and the great guns, with every precaution, after some 

 years become useless. Stones, as being less hard, may be 

 readily supposed to be more easily soluble. The marble of 

 which the noble monuments of Italian antiquity are composed, 

 although in one of the tinest climates in the world, show the im- 

 pressions which have been made upon them by the air. In 

 many places they seem worm-eaten by time ; and in others, 

 they appear crumbling into dust. Gold alone seems to be ex- 

 empted from this general state of dissolution ; it is never found 

 to contract rust though exposed never so long : the reason of 

 this seems to be, that sea-salt, which is the only menstruum 

 capable of acting upon and dissolving gold, is but very little mix- 

 ed with the air ; for salt being a very fixed body, and not apt to vo- 

 latilize, and rise with heat, there is but a small proportion of it 

 in the atmosphere. In the elaboratories and shops, however, 

 where salt is much used, and the air is impregnated with it, 

 gold is found to nist as well as other metals. 



Bodies of a softer nature are obviously destroyed by the air.' 

 Mr Boyle says, that silks brought to Jamaica, will, if there ex- 

 posed to the air, rot, even while they preserve their colour ; but 

 if kept therefrom, they both retain their strength and gloss. The 

 same happens in Brazil, where their clothes, which are black, 

 soon turn of an iron colour ; though in the shops, they preserve 

 their proper hue.' In these tropical climates also, such are; the 

 putrescent qualities of the air, that white sugar will sometimes 

 be full of maggots. Drugs and plasters lose their virtue, and 

 become verminous. In some places they are obliged to expose 

 their sweetmeats by day in the sun, otherwise the night-air 

 would quickly cause them to putrify. On the contrary, in 

 the cold arctic regions, animal substances, during the winter 



1 BuffoD, vol iii. p. IT2 2 Ibid. vol. iii. p. 6& 



