TOE DYNAMICAL EVIDENCE OF THE 



had developed with the utmost generality the dynamical theory of a material 



yatem. 



Of all hypotheses as to the constitution of bodies, that is surely the most 

 warrantable which assumes no more than that they are material systems, and 

 im|i|ujju to Deduce from the observed phenomena just as much information about 

 the conditions and connections of the material system as these phenomena can 



legitimately furnish. 



When examples of this method of physical speculation have been properly 

 act forth and explained, we shall hear fewer complaints of the looseness of the 

 reasoning of men of science, and the method of inductive philosophy will no 

 longer be derided as mere guess-work. 



It is only a small part of the theory of the constitution of bodies which 

 has as yet been reduced to the form of accurate deductions from known facts. 

 To conduct the operations of science in a perfectly legitimate manner, by means 

 of methodised experiment and strict demonstration, requires a strategic skill 

 which we must not look for, even among those to whom science is most in- 

 debted for original observations and fertile suggestions. It does not detract from 

 the merit of the pioneers of science that their advances, being made on unknown 

 ground, are often cut off, for a time, from that system of communications 

 with an established base of operations, which is the only security for any per- 

 manent extension of science. 



In studying the constitution of bodies we are forced from the very be- 

 ginning to deal with particles which we cannot observe. For whatever may be 

 our ultimate conclusions as to molecules and atoms, we have experimental proof 

 that bodies may be divided into parts so small that we cannot perceive them. 



Hence, if we are careful to remember that the word particle means a small 

 part of a body, and that it does not involve any hypothesis as to the ultimate 

 divisibility of matter, we may consider a body as made up of particles, and 

 we may also assert that in bodies or parts of bodies of measurable dimensions, 

 the number of particles is very great indeed. 



The next thing required is a dynamical method of studying a material 

 system consisting of an immense number of particles, by forming an idea of their 

 configuration and motion, and of the forces acting on the particles, and deducing 

 from the dynamical theory those phenomena which, though depending on the 

 configuration and motion of the invisible particles, are capable of being observed 

 in visible portions of the system. 



