722 REPORT— 1889. 



in bodies so as to produce the effects of heat directly applied; it is capable of 

 setting up motions of sucli intensity as to produce clieiuical changes and decom- 

 positions, to say nothing of the whole series of phenomena connected with 

 magnetism, with induction, or the action through space and through non-con- 

 ducting bodies, which, as in the case of radiant heat and light, seems to imply the 

 existence of an interatomic ether, Conversely, changes of molecular equilibiium, 

 brought about by the action of external forces, produce corresponding changes in 

 electrical currents : witness the effects of heat, for example, on conductivity and the 

 wondrous revelations of molecular change obtained by the aid of Professor Hughes's 

 induction balance. The behaviour of explosives illustrates also, and in a striking 

 manner, the effects of disturbing molecular equilibrium. iVn explosive is a sub- 

 stance which contains in itself, in a solid or liquid form, all the elements necessary 

 to produce a chemical change by which it is converted into the gaseous state. The 

 application of heat, of pressure, or of impact, causes, as in Professor Spring's ex- 

 periments, chemical union to take ]jiace, hrst at the spot where the equilibrium is 

 disturbed by the application of external force, and afterwards, with great rapidity, 

 throughout the mass, the disturbance being propagated either by the air surround- 

 ing the particles or by the luminiferous ether, with all the rapidity of light; the 

 chemical reaction is accelerated by the pressure which ma}^ arise, for example, if 

 the explosive be confined in the chamber of a gun or in the bore-hole of a blast. 

 High explosives, as they are termed, are comparatively inert to ordinary ignition ; 

 but when the molecular equilibrium is suddenly disarranged throughout the mass 

 by the detonation of a percussion fuse, combination takes place instantlj' throughout, 

 and violent explosion follows. In a similar manner some gases, such as acetylene, 

 CN'anogen, and others, can be decomposed by detonation and reduced to tlieir solid 

 constituents. Professor Thorpe has devised a very beautiful lecture e.xperiment, in 

 which carbon disulphide is caused to fall asunder into carbon and sulphur by the 

 detonation of fulminate of mercury fired by an electric spark. In these cases a 

 reverse action takes place, but illustrates equally well the conversion of one form 

 of energy into others, and the consequent disturbance of molecular equilibrium in the 

 substances affected. It seems to me clear, therefore, that the time has come when 

 the conception of dynamic equilibrium in the ultimate particles of matter in all its 

 forms must take the place of the structural system of inert particles. I cannot 

 conceive how the phenomena which I have enumerated can be explained on the 

 supposition that matter is built up of motionless particles — how, for example, a 

 stack of red and yellow bricks could ever change the order of arrangement without 

 being completely pulled asunder and built up again, iu which case an intermediate 

 state of chaos would exist ; but I can easily comprehend how a dense crowd of 

 people may appear as a compact mass, streaming, it may be, in a definite direction, 

 and yet how each member of that mass is endowed with limited motion, by virtue 

 of which he may push his way through without disturbing the general appearance ; 

 how the junction of two crowds would form one whole, though, perchance, altered 

 in character ; and how even Professor Spring's experiments may be explained by 

 the supposition that bystanders on the edge of a crowd would be forced, by external 

 pressure, to form part of it and partake of its general movements. 



It is a suggestive fact that the product of the atomic weight of certain groups 

 of substances and their specific heats is a constant quantity which, for the greater 

 number of the elements, does not differ much from 6'5. This implies that the 

 quantity of heat necessary to raise the temperature of the atoms of any one of the 

 groups to any given extent is the same ; hence these atoms will be endowed with 

 the same amount of energy at any given temperature, and therefore would be com- 

 petent to replace each other without disturbing the general dynamic equilibrium. 



When it is conceded that molecular motion pervades matter in all its forms, and 

 that the solid passes, often insensibly, into the fluid, or even direct into the gaseous, 

 it follows, almost of necessity, that there must be a borderland, the limits of which 

 are determined by temperature and pressure, in which substances are constantly 

 changing from one state to another. This is observable in fusion, but to a more 

 marked degree in evaporation, where the particles are being incessantly launched 

 into space as gas and return as constantly to the liquid state. Henri St. Claire 



