2 3 2 POPULAR LECTURES AND ADDRESSES. 



alluded, did not exist, and if we could be per- 

 fectly satisfied with the kinetic theory of gases 

 founded on the collisions of elastic solid mole- 

 cules, there would still be beyond it a grander 

 theory which need not be considered a chimerical 

 object of scientific ambition to explain the 

 elasticity of solids. But we may be stopped 

 when we commence to look in the direction of 

 such a theory with the cynical question : What 

 do you mean by explaining a property of matter ? 

 As to being stopped by any such question, all 

 I can say is that if engineering were to be all 

 and to end all physical science, we should perforce 

 be content with merely finding properties of 

 matter by observation, and using them for 

 practical purposes. But I am sure very few, 

 if any, engineers are practically satisfied with so 

 narrow a view of their noble profession. They 

 must and do patiently observe, and discover by 

 observation, properties of matter, and results of 

 material combinations. But deeper questions are 

 always present, and always fraught with interest 

 to the true engineer, and he will be the last to 



