I 



PRIMARY CONCEPTS OF MODERN SCIENCE. 219 



THE PPwIMARY CONCEPTS OF MODERN PHYSICAL 



SCIENCE. 



By J. B. STALL 0. 

 III. — The Assumption of the Essential Solidity of Matter. 

 T cannot have escaped the notice of the attentive reader of the 



passage quoted irf my last paper from Prof. Tyndall's lecture on 

 " The Use of the Scientific Imagination " that Tyndall urges the 

 theory of the atomic constitution of matter as the only theory con- 

 sistent with its objective reality. He takes it for granted that the 

 alternative lies between the definite, tangible, solid atom on the one 

 hand, and a shadowy abstraction — a " vibrating, multiple proportion, 

 or a numerical ratio in a state of oscillation " — on the other. There 

 is no doubt that the opinion thus expressed is shared by the great ma- 

 jority of physicists, as well as of ordinary untrained men. To the 

 minds of most persons, as to the mind of Tyndall, the conception of 

 matter involves the notion of definite, tangible, and indestructible 

 solidity. It is the general tacit assumption that, of the three molecu- 

 lar states, or states of aggregation, in which matter presents itself to 

 the senses — the solid, the liquid, and the gaseous — the last two are 

 simply disguises of the first ; that a gas, for instance, is in fact a 

 group or cluster of solids, like a cloud of dust, differing from such a 

 cloud only by the greater regularity in the forms and distances of the 

 particles whereof it is composed, and by the fact that these particles 

 are controlled in the case of a gas by their mutual attractions and re- 

 pulsions, while in the case of the cloud of dust they are under the 

 sway of extrinsic forces. And, while the transition of the three 

 molecular states into each other in regular and invariable order is too 

 obvious to be ignored, it is supposed that the solid is the primary, 

 normal, and typical state of which the liquid and gaseous, or aeri- 

 form, states are simply derivatives, and that, if these states are con- 

 sidered as evolved the one from the other, the order of evolution is 

 from the solid to the vapor or gas. In this view the solid form of 

 matter is not only the basis and origin of all its further determinations 

 — of all its evolutions and changes — but it is also the primary and 

 typical element of its mental representation and conception. 



While this view of the relation between the molecular states of 

 matter is all but universally prevalent, it is not difficult to show that 

 it is in irreconcilable conflict with the facts of scientific experience. 

 All evolution proceeds from the relatively Indeterminate to the rela- 

 tively Determinate, and from the comparatively Simple to the compara- 

 tively Complex. And (confining our attention, for the moment, to the 

 two extreme terms of the evolution, the solid and the gas, and ig- 



