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viz. that all the phenomena which we can contemplate are as they 

 are determined by their proper causes: thus, there are some causes 

 which, uniting in combination, form certain chymical properties ; 

 there are other causes which determine the alliance between these 

 chymical, and the mechanical properties of matter. But this ap- 

 pears to be a mere, though perhaps an invariable association ; for if 

 chymical properties produced in the way of true constitution the com- 

 mon ones of matter, then should the uniformity of the latter require 

 uniformity of the former, which is not the fact; and if the common 

 produced the chymical properties of matter, then as the former are 

 common so also should be the latter, which again is not the fact. 

 Hence we may say safely, that these sets of properties are conjoined 

 in their respective specimens ; and proceed to indicate a little further 

 some results of this union. 



10. The chymical properties of substances are not capable of 

 being directly altered by mechanical agency ; this latter may give 

 motion, or it may compress or separate the parts of the former: but 

 if, after a mechanical agency upon the substance, its chymical proper- 

 ties are changed, it will be by a new relation which is opened be- 

 tween them and others of the same class. As when a solid body is 

 extenuated to a mere surface, its atmospherical exposure is more 

 complete, and changes may then occur in it which would not have 

 taken place before, at least, in the same time. 



11. But the common appear liable to be directly changed by 

 an influence on the peculiar properties of substances. Thus a solid 

 body by chymical relations may be rendered fluid, or converted 

 into gas ; and although in this case the properties of matter would 

 not be lost, but would still be associated with the chymical proper- 

 ties, yet it cannot be denied but, as mechanical agents, the common 

 properties of matter are very different in the two states : in the one 

 it resists the impulse of other substances, or is itself put in motion, 

 and again communicates the impulse of a solid body to others of 

 its own kind; but, after its conversion, it yields to the substances 

 which it would before have resisted, and neither takes nor communi- 

 cates motion, &c. It may be contended, as 1 am aware, that all 

 these varieties are only modifications of matter, or of extension ; 

 but this doctrine is completely refuted (which is saying a great deal) 

 in the chapter on Causation. 



12. The common substances of nature, being provided with these 

 two sets of properties, we find these in animal bodies still more 

 complicated by another class of properties, which are not common 

 to substances considered either in their mechanical or chymical 

 nature, or in both. Sufficient has been said of these properties : it 

 remains only to add, 1st, that spiritual properties are related with. 

 others of their own kind ; 2nd, that as the cbymical are allied with 

 common properties of matter, so the spiritual are allied with both ; 

 3rd, that whereas the common cannot change the chymical proper- 

 ties of matter, neither can they the spiritual; but the class of chy- 

 mical agents, having in alliance spiritual properties (for they maintain 



