from Dr. Thornton. e^ig 



tlie texture of their food is uot rightlv changed in tlicir bo- 

 dies hy heat and motion ; which niay be o\\ nag either to 

 an uniiuiess in the food for such a change, or to degrees of 

 heat and motion unlit to eflect it. 



" Proposition xxix. — The coiiditiient solid parts of ani- 

 mals, according Jo tkeir several mti/res, arc endued with 

 pecidiur attr<iciive powers of certain magnitudes or strengths, 

 li/ which theij draw out of the Jiiddi msvi?/g through them 

 like parts in certain quantities, and thereby preserve their 

 forms and just magnitudes. 



" For, withoutattractive powers agreeable to their na- 

 tures, the constituent sohd parts of animals cannot draw- 

 like particles out of the fluids moving through them, and 

 •conscfjuently cannot preserve their forms ; and unless these 

 powers be of certain strengths, they cannot draw tiiose parts 

 in such (juantities as arc proper to preserve tlieir magni- 

 tudes : and therefore the proposition is true. 



" Cor. 1, Heirce bodies will not be rightly nourished by 

 proper food, changed by just degrees of heat and motion, 

 w hen the attractive powers of their solid parts ai.c changed 

 either in their natures or in their magnitudes^ 



'^ Cor. 2- Hence anijnals of the same species will grow 

 faster or slower out of the same nourishment rightlv changvd 

 by heat and motion, as the attractive powers i)f their solid 

 parts arc stronger or weaker : and universally their growtli 

 in a given time will be greater or less, as the attractive 

 powers of corresponding parts arc greater or less ; or as the 

 fluids moving through those parts al)ound more or less with 

 similar particles, that is, with particles rightly fitted to be 

 attracted by those powei-s. 



** General SchoUunu 



^' I have shown that die nourishment of animals becomes 

 more dry and earthy in their bodies, and that this change is 

 effected by a gentle heat and motion. How a gentle heat 

 and motion cause this change in the nourishment, may be 

 understood from what Sir Isaac Newton has delivered con- 

 cerning the nature of salt. This great man, finding from 

 experiments and observations that sahs are dry earth and 

 watry acid united bv attraction, and that the earth will not 

 become a salt without so much acid as makes it dissolvable 

 in water, has given tlxe following account of the formation 

 of particles of salt : 



" ' As jrnivitv makes the sea flow round the denser and 



weightier parts of the globe of the earth, so the attraction 



may make the watry acid ilow round the denser and com- 



pacler particles of earth for composing the particles of salt : 



1^ 3 for 



