212 SPECULATIVE SCIENCE 



mathematical machinery by which we can test how completely 

 any hypothesis does fulfil those conditions. The materials for 

 the work are not wanting, though the architect has not ap- 

 peared. Inertia and motion seem the most indispensable ele- 

 ments in the conception of the materia prima extended in space. 

 Once in motion, it must continue in motion till stopped ; when 

 at rest, it must not move without a cause ; when in motion, it 

 represents energy, or power, and can exert force. How ? The 

 simplest but not the only mode conceivable, is by displacement, 

 in virtue of the property that two parts of it cannot occupy one 

 and the same part of space. The believers in displacement may 

 assume that space is quite full, or that in parts it is wholly 

 empty ; that it contains one, two, or more kinds of primary in- 

 gredients capable of displacing one another, or each its own 

 products merely. 



The most plausible suggestion yet made by this school is, 

 that a single omnipresent fluid, ether, fills the universe ; that 

 by various motions, of the nature of eddies, the qualities of co- 

 hesion, elasticity, hardness, weight, mass, or other universal pro- 

 perties of matter are given to small portions of the fluid which 

 constitute the chemical atoms ; that these, by modifications in 

 their combination, form and motion, produce all the accidental 

 phenomena of gross matter ; that the primary fluid, by other 

 motions, transmits light, radiant heat, magnetism, and gravita- 

 tion ; that in certain ways the portions of the fluid transmuted 

 into gross matter can be acted upon by the primary fluid which 

 remains imponderable or very light ; but that these ways differ 

 very much from those in which one part of gross matter acts 

 upon another; that the transmutation of the primary fluid into 

 gross matter, or of gross matter into primary fluid, is a creative 

 action wholly denied to us, the sum of each remaining constant. 



Gross matter, on this view, would be merely an assemblage 

 of parts of the medium moving in a particular way ; groups of 

 ring-vortices, for instance. There appears to be some difficulty 

 in determining the fundamental properties to be assumed for our 

 medium. We must grant it inertia or it would not continue in 

 motion. 



The believers in hard atoms can hardly restrict themselves to 

 the combination and motion of atoms of gross matter; these will 



