ON CHEMICAL ATTRACTION. 



193 



minatioii of ^liferent parts of the solar disk, show, that thje 

 degree of illumination of the edges and of the centre is 

 precisely the same, contrary to the opinion generally re- Og^j^. ^ * 

 ceived. Mr. Clement has very happily applied prof. Leslie's animal and re- 

 process for the formation of ice to the rapid and complete ftaitccs^^ 

 dessiccation of various animal and veu:etable substances, fie p,. ^, .. 

 has also greatly improved the apparatus for evaporating li- 

 quids by the help of fire. 



VIII. 



On Chemical^tlraction. By Marshall Hall» Esq, 

 T['o W.NICHOLSON, Esq. 



G 



SIR, 



'HEMICAL attraction is that force, by which the parti- Chemical »»- 

 cles of matter are drawn towards each other. These parti- ^■^**^"''"* 

 cles are of two kinds ; for they maybe similar to each other, 

 as in the same simple body, when they are termed homo- 

 geneous; or they may be dissimilar, as in a compound 

 body, and are then denominated heterogeneous. From this 

 distinction between the particles of material objects, a divi- 

 jiion of the attraction, which unites them, immediately flows. 

 The force, which occasions similar particles to cohere, is called 

 homogeneous attraction ; dissimilar particles are united by Homogeneotis 



heterogeneous attraction : the former is the cause of co- ^^ hetem- 



. . . , . . . geneousattrac- 



hesion in simple bodies; the latter occasions combination tion. 



between different bodies. 



But, beside these, philosophers have supposed, that a A third order 

 third order of particles, and of attraction, influences che- ° ''^"^"i^^j*^!.^ 

 rnical actions. " Heterogeneous affinity urges heterogene- tion supposed. 

 *' ous particles toward each other, and of course is the cause 

 *' of the formation of new integrant particles^ composed of 

 " a certain number of heterogeneous particles. These new 

 *• particles afterward unite by cohesion, and form masses of 

 " compound bodies*." lii the words of Mr. Murray, «' the 

 ** iutegiant particles are merely the smallest particles, into 

 * Thomsson, ed. 3, Tol. lllj p. 408. 



Vol. XXX Nov. 1811. O " whiuh 



