470 Mr. W. Crookes. On a Fourth State of Matter. [June 10, 



molecules diminishes ; and were there no other counteracting force the 

 result would be a mass of molecules in actual contact, with no mole- 

 cular movement whatever — a state of things beyond our conception — 

 a state, too, which would probably result in the creation of something 

 that, according to our present views, would not be matter. 



This force of cohesion is counterbalanced by the movements of the 

 individual molecules themselves, movements varying directly wibh the 

 temperature, increasing and diminishing in amplitude as the tempera- 

 ture rises and falls. The molecules in solids do not travel from one 

 part to another, but possess adhesion and retain fixity of position about 

 their centres of oscillation. Matter, as we know it, has so high an 

 absolute temperature that the movements of the molecules are large in 

 comparison with their diameter, for the mass must be able to bear a 

 reduction of temperature of nearly 300° C. before the amplitude of 

 the molecular excursions would vanish. 



The state of solidity therefore — the state which we are in the habit 

 of considering par excellence as that of matter — is merely the effect on 

 our senses of the motion of the discrete molecules among themselves. 



Solids exist of all consistences, from the hardest metal, the most 

 elastic crystal, down to thinnest jelly. A perfect solid would have no 

 viscosity, i.e., when rendered discontinuous or divided by the forcible 

 passage of a harder solid, it would not close up behind and again 

 become continuous. 



In solid bodies the cohesion varies according to some unknown factor 

 which we call chemical constitution ; hence each kind of solid matter 

 requires raising to a different temperature before the oscillating mole- 

 cules lose their fixed position with reference to one another. At this 

 point, varying in different bodies through a very wide range of tem- 

 perature, the solid becomes liquid. 



II. In liquids the force of cohesion is very much reduced, and the 

 adhesion or the fixity of position of the centres of oscillation of the 

 molecules is destroyed. When artificially heated, the inter-molecular 

 movements increase in proportion as the temperature rises, until at 

 last cohesion is broken down, and the molecules fly off into space with 

 enormous velocities. 



Liquids possess the property of viscosity — that is to say, they offer 

 a certain opposition to the passage of solid bodies ; at the same time 

 they cannot permanently resist such opposition, however slight, if con- 

 tinuously applied. Liquids vary in consistency from the hard, brittle, 

 apparently solid pitch, to the lightest and most ethereal liquid capable 

 of existing at any particular temperature. 



The state of liquidity, therefore, is due to inter-molecular motions of 

 a larger and more tumultuous character than those which characterise 

 the solid state. 



III. In gases the molecules fly about in every conceivable direction, 



