in Fluids. 383 



and as it is known that an oxyd of gold may be reduced 

 in the dry way without addition, or merely by intense 

 Heat, why should we not conclude that it is merely by 

 Heat that that metal is revived in the case under con- 

 sideration, and that the intensity of the Heat by which 

 this oxygenation is effected is precisely the same in both 

 cases ? . . 



Should this supposition be admitted, we might, per- 

 haps, venture to proceed one step farther, and consider 

 the nature and progress of the mechanical operations 

 which take place in disoxygenation of metals, or their 

 precipitation from a solution of their oxyds, when that 

 operation is effected by means of Heat generated, not 

 by light, but by the contact or union of infinitely 

 small particles of bodies, different in kind, and disposed 

 to generate or to absorb sensible Heat on coming to- 

 gether ; which particles being dispersed about in the 

 liquid solution, and in the substance added to it to 

 effect the precipitation, are by this mixture brought into 

 contact. 



This would naturally lead us to an examination of the 

 phenomena of solution ; and those clearly understood 

 would, no doubt, give us a distinct view of the mechani- 

 cal operations by which those tendencies to union are 

 effected which have been designated under the name 

 elective attraction. 



But how arduous an undertaking ! what intense 

 study ! what efforts of the imagination would be neces- 

 sary to trace out and form distinct ideas of such a suc- 

 cession of events, all perfectly imperceptible by our or- 

 gans, though assisted by all the resources of art ! 



Sensible of my own weakness, I dare not proceed any 

 farther. Perhaps it will be thought that I have already 



