18 CHEMISTRY AND PHYSICS H* DELATION 



relation to certain phenomena, observed in inanimate nature, I do it much less 

 with the desire of advancing any new views regarding the nature and substance 

 of contagion and miasma, or bringing forward the question of fermentation and 

 putrefaction, than of drawing the attention of naturalists to a cause which, although 

 hitherto ill observed, is one that prevails generally, wherever a change occurs in 

 the form and property of matter, or wherever combination and decomposition are 

 going on. And if proof be adduced, that this cause exercises a decided and refer- 

 able influence upon the indication and direction of the forces of cohesion and 

 affinity, its undeniable share in the actions of vital force will be the less ques- 

 tioned, since vital force belongs to the same category as chemical forces, as far as 

 the former manifests its activity only by direct contact, or at immeasurably small 

 distances. 



INFLUENCE OF MECHANICAL MOTION ON CRYSTALLIZATION. 



Every one knows that water freezes at all temperatures below 32 F., and that 

 during the act of freezing the temperature remains at 32 F. ; nevertheless, water 

 may be cooled as low as 5 F., without becoming solid, if the fluid be in a state 

 of perfect rest. The least disturbance is sufficient to effect congelation. 



INFLUENCE OF MECHANICAL MOTION ON CRYSTALLIZING SOLU- 

 TIONS OF SALTS. 



The same conditions affect a number of solutions of salts, dissolved by heat; 

 if cooled in a state of perfect rest they do not precipitate any salts, and no separa- 

 tion occurs between the water and the dissolved salt, while the least disturbance 

 a particle of dust or a grain of salt thrown into the water will induce the mole- 

 cules thus disturbed to crystallize, and when once crystallization has begun, it is 

 continued throughout the whole mass. 



INFLUENCE OF MECHANICAL MOTION ON SULPHURET OF MER- 

 CURY, IODIDE OF MERCURY, AND IRON. 



By constant shaking and friction, the black amorphous suphuret of mercury is 

 converted into crystalline cinnabar, while the rough iron, whose parts are irregu- 

 larly deposited, becomes crystalline on being hammered. On rubbing a portion 

 of lemon colored iodide of mercury, it passes into a new state of crystallization, 

 and becomes scarlet. 



From these facts it is shown that a mechanical motion exercises an influence 

 upon the indication of the force which governs the condition of the body, and this 

 motion is continued to its smallest molecules ; for the formation of crystals it is 

 necessary that they should be turned towards the direction in which the force of 

 attraction is the strongest; it is, therefore, clear that atoms can be put in motion in 

 fluids, as well as in solid bodies, by a stroke or blow, by frictic>n, or by some other 

 meehanical cause. The causes do not, however, exercise a certain influence on 

 the indication of the cohesive power alone, but also upon the chemical affinity. 



INFLUENCE OF MECHANICAL MOTION ON THE INDICATION OF 

 CHEMICAL AFFINITY. 



In a weak solution of chloride of potassium, tartaric acid does not deposit any 

 piecipitate : but mere shaking, or the friction of the inner wall of the ves^H * "'** 



