230 Letter to Governor PownalL 



for otherwise the acid would not do the office of a medium 

 between the earth and common water, for making salt? dis- 

 solvable in water; nor would salt of tartar readily draw off 

 the acid from dissolved metals, nor metals the acid from 

 mercury. Now, as in the great slobe of the earth and sea 

 the densest bodies by their gravity sink down in water, and 

 always enrJeavovir to go tow aids the centre of the globe, so 

 in particles of salt the densest matter may always endeavour 

 to approach the centre of the particle : so that a particle of 

 salt may be compared to a chaos, being dense, hard, dry, 

 and earthy in the centre ; and rare, soft, moist, and watry, 

 in the circumference. And hence it seems to be that salts 

 are of a lasting nature, being scarce destroyed, unless by 

 drawing away their watry parts by violence, or by letting 

 them soak into the pores of the central earth by a gentle 

 heat in putrefaction, until the earth be dissolved by the water 

 and separated into smaller particles, which by reason of 

 their smallness make the rotten compound appear of a black 

 colour. Hence also it may be that the parts of animals* 

 and vegetables preserve their several forms, and assimilate 

 their nourishment ; the soft and moist nourishment easily 

 changing its texture by a gentle heat and motion, till it be- 

 comes like the dense, hard, dry, and durable earth in the 

 centre of each particle. But when the nourishment grows 

 unfit to be assimilated, or the central earth grows too feeble 

 to assimilate it, the motion ends in confusion, putrefac- 

 tion, and death.'" — Newt. Opt. p. 361, 302. 



*' Hence it appears that to render the saline part of the 

 aliment fit to nourish the solid parts of animals and vegeta- 

 bles, part of the superficial watry acid must by heat and 

 motion be drawn off from the particles of salt, by which 

 they W'ill become more dense, hard, dry, and earthy, like 

 the solid and durable parts of the bodies : and, according 

 to the ditferent degrees of heat and motion in the dit^erent 

 species of animals and vegetables, the watry moisture will 

 be drawn off in dificrent proportions, so as in each species 

 to render the particles like the solid parts of the bodies of 

 that species. 



" And further, if we consider that water is a very fluid taste- 

 less salt, and that animals ar.d vegetables, with their several 

 parts, grow out of water and watry tinctures and salts, we 

 may, from w-hat has been said, understand the manner in 

 which the nourishment of animals and vegetables is changed 

 by a gentle heat and motion till it become like the solid and 

 durable parts of their respective bodies. 



*' Proposition xxx. — The glanch in the hodies of an'imah:, 



accordi/ig 



