1 1 Eleftive Altratthn. [Book I. 



the effect is not owing to the prefiure of the air. In 

 the fame manner, alfo, by the fame law, fluids will 

 afcend in the cavity of a fponge, in the interftices of 

 linen cloth, or any porous body. 



II. The attraction of COMBINATION, or chemical 

 or elective attraction, is in many refpects analogous 

 to the attraction of cohefion. Like the latter, it feems 

 to depend on the minute particles of bodies being 

 brought nearly into contact with each other ; and in- 

 deed fo nearly alike are the effects of thefe two fpe- 

 cies of attraction, that if they are different in prin- 

 ciple, it is difficult to fay which is the moft eflential 

 to the cohefion and folidity of bodies *. Chemical 

 attraction may probably be no other than the attrac- 

 tion of cohefion acting in a free and unrefifting me- 

 dium, fmce its only diftinguifhing characteriftic is the 

 difpofition which bodies in folution indicate to unite 

 with certain fubftances in preference to others. To 

 make this clear by an experiment If a quantity of 

 filver is added to a quantity of aqua fortis, the cohe- 

 fion of the particles of the filver will be ckftroyed, and 

 they will unite forcibly with thofe of the aqua fortis. 



* The two fpecics of attraction are well defiued by Bergman : 

 that which he calls the attraction of aggregation, I clafs under 

 that of cohefion; that which he calls compofition, I call combina- 

 tion. When an increa'fe of mafs only takes place, the nature of 

 the body remaining ftill the fame, this cifed is denominated the 

 attraction of aggregation. But heterogeneous fubftances, when 

 mixed together, and left to themfelves to form combinations, are 

 influenced by difference of quality rather than of quantity. 

 This we call attraction of comj>cfition, and when it is exerted in 

 forming a mere union of two or more fubftances, it receives the 

 name of attraction of folution ovfufion, according as it is effected 

 either in the moift or dry way. When it takes place between 

 three refpedively, to the exclufion of one, it is faid to be a/.v- 

 glt eleSi'vt attraction, and when between two compounds, .a dou- 

 ble, &c.' Berg, on Elcc. Atu. i. 



The 



