On Chemical Philosophy/. 3 JO 



peiui< on rendering this power too dense to escape through the 

 apparatus as it would do in its pure state. Its power is in pro- 

 portion as its radiating energies are unoccupied, and yet suffi- 

 ciently confinable not to pass through the vessel*; thence the 

 powers of the air-machine lately discovered, (I conceive the 

 word discovered is more correct than invented: the power is the 

 discovery; the wheels, and pinions,&:e. are the invention,) or, as 

 it has been called, the rarefied air-machine. What is called the 

 elasticity and compressibility of air is heat, or this power pass- 

 ing out and passing in : if altogether separated by compressioa 

 from the substance held in solution, as in the German tinder-box, 

 its elasticity instantly ceases. In short, not to dwell more om 

 these points at present, it seems to me that certain appropriate 

 quantities are inherent in all passive substances, and may there- 

 Jore, probably, bind them together ; and that all above this 

 leiids to dissolve and change their state of existence from the 

 5olid to the liquid, and from the liquid to the gaseous state ; and 

 if not soluble, to separate their parts or particles, more or less, 

 according to circumstances. As for instance, a change of elec- 

 tricity will explode a small quantity of water, converting it into 

 vapour; and if confined in a small tube, burst it with explosion, 

 or cause pith-balls which are not soluble to diverge, &c. 



Tlie action of one quantity or proportion of this power, I 

 therefore say, is necessary to the present relative order of things; 

 and according to this order, and this state, is confined principally 

 to the internal parts, and preserves and supports them in this 

 relative and present form of existence. The other, or additional 

 proportion, is the excess, and has the power more obviously of 

 dissolving and uniting, or moving and separating particles and 

 masses, carrying in one direction, and drawing in another. And 

 in proportion to their solubility or insolubility they are united or 

 separated from each other. 



The first, or combined quantity, more particularly pervades 

 passive substances throughout space. The last, theuncombineil 

 quantity, more particularly pervades space void of passive sub- 

 stances, and is the infinite medium or stupendous chain of con- 

 nexion between them. This distinction, then, though it may 

 in some measure be arbitrary and artificial ; vet it comes ne;;r 

 to facts, and the natural state of things ; and it is one which I 

 think will be found useful in assisting the memory, the only u^e 



• This and every part of this view or theory of the subject was entertained 

 in 1S06, as may be proved l)y a correspondence with the late Dr. Fawcett, 

 in Chester, if these letters are stiil in existence. I mention this, because 

 many improvements in the steam-engine prove this view correct. 1 o 

 speak of the expansive power of steam, convey.s to me a very inipcrloi.t ami 

 inad(.(iuate explanation of the mode of its acUon. 



of 



