Atmolysis. 41 7 



These considerations of these phenomena have led Mr. 

 Graham into certain speculations respecting the constitution 

 of matter. It is conceivable that the various kinds of matter, 

 now regarded as different elementary substances, may possess 

 one and the same ultimate molecules in different conditions of 

 movement. The essential unity of matter is a hypothesis in 

 harmony with the uniform action of gravity on all bodies; we 

 may imagine one substance only to exist, namely, ponderable 

 matter, and that this is divisible into ultimate atoms, uniform 

 in size and weight ; if these atoms were at rest the uniformity 

 of matter would be perfect. But they always possess more 

 or less motion due to some original primordial impulse; 

 this motion gives rise to volume ; the more rapid the 

 motion the greater the space occupied by the atom. Thus, 

 matter of different density forms different substances, that are 

 usually regarded as different inconvertible elements, and this 

 hypothesis may be pursued through the various phases of 

 combination ; the different states of solid, liquid, and gas, and 

 the colloid and crystalline forms of matter. 



Recent as are these discoveries and speculations of the 

 author, they have already a practical bearing on the commu- 

 nication of heat to or from gas or vapours, by contact with solid 

 or liquid surfaces ; for the impact of the gaseous molecule on a 

 surface possessing a different temperature from itself appears 

 to be a condition of the transference of heat from one to the 

 other. The more rapid the molecular movement of the gas, the 

 more frequent the contact, and, consequently, the more rapid 

 the communication of heat. Hence, the great cooling power of 

 hydrogen as compared with that of air or oxygen. These 

 gases have the same capacity for heat, as regards equal 

 volumes ; but a hot body placed in hydrogen is really touched 

 3*8 times more frequently than it would be if placed in air, and 

 4 times more frequently than it would be in an atmosphere 

 of oxygen. This property of hydrogen recommends the appli- 

 cation of that gas to the air or caloric engine, where the object 

 is alternately to heat and cool a confined volume of gas with 

 great rapidity. 



There can be no doubt but that engines worked by steam, 

 the employment of which is always attended with so great a 

 loss of heat, will eventually be superseded by air or caloric 

 engines, where there is no ]oss by condensation. Theoretically, 

 air engines are perfect, and the practical difficulties that pre- 

 vented their adoption are being gradually overcome. 



