II THE PROGRESS OF SCIENCE 67 



In the early decades pf this century, a number 

 of important truths applicable, in part, to matter 

 in general, and, in part, to particular forms of 

 matter, had been ascertained by the physicists and 

 chemists. 



The laws of motion of visible and tangible, or 

 molar, matter had been worked out to a great 

 degree of refinement and embodied in the branches 

 of science known as Mechanics, Hydrostatics, and 

 Pneumatics. These laws had been shown to hold 

 good, so far as they could be checked by observa- 

 tion and experiment, throughout the universe, on 

 the assumption that all such masses of matter 

 possessed inertia and were susceptible of acquiring 

 motion, in two ways, firstly by impact, or impulse 

 from without ; and, secondly, by the operation of 

 certain hypothetical causes of motion termed 

 ''forces," which were usually supposed to be 

 resident in the particles of the masses themselves, 

 and to operate at a distance, in such a way as to 

 tend to draw any two such masses together, or to 

 separate them more widely* 



With respect to the ultimate constitution of 

 these masses, the same two antagonistic opinions 

 which had existed since the time of Democritus 

 and of Aristotle were still face to face. According 

 to the one, matter was discontinuous and consisted 

 of minute indivisible particles or atoms, separated 

 by a universal vacuum ; according to the other, it 

 was continuous, and the finest distinguishable, or 



F 2 



