144 SCIENTIFIC THOUGHT. 



bringing them into harmony and continuity with the 

 older Newtonian ideas. These had been only imper- 

 fectly transmitted by the many commentaries and text- 

 books of the Cambridge school. The same was the 

 case in the system of Lagrange, in which the whole 

 of mechanics had been reduced to a mathematical ex- 

 pression, the physical and experimental foundations 

 being pushed aside. The ' Principia ' of Newton was 

 again studied, and re -edited in the unabridged form, 

 and an interpretation and amplification of the third 

 law of Motion so as to embrace the principle of 

 energy was made the key to the science of dyn- 

 amics. Dynamics was not taught after but before 

 statics. Statics was treated as a special case of the 

 theory of motion. To make the new position still 

 more marked, it was proposed to make the term 

 dynamics the general term which embraces kinetics 

 and statics as subdivisions, and to reserve the word 

 " mechanics " for the science of machines. The change 

 which then took place in the didactic methods can 

 be seen by comparing the first and second editions of 

 the well-known treatise by Tait and Steele on ' The 

 Dynamics of a Particle.' The real compendium of the 

 new doctrine is the treatise on Natural Philosophy by 

 31. Thomson and Tait, which has probably done more than 



Thomson . 



and Tait. any other book in this country to lead the mathe- 

 matical studies at the foremost universities and colleges 

 into paths more useful for physical and experimental 

 research. The greatest exponent of the new ideas was 

 James Clerk Maxwell, to whom is also due the merit 

 of having applied them for the purpose of testing and 



