64 UNIVERSITY OF MISSOURI BULLETIN 



deduced when the laws of mechanics were appHed to elec- 

 trical problems. Today we have a subject, sometimes called 

 the mathematical theory of electricity and magnetism, which 

 is an application of the principles and methods of mechanics 

 and is a further extension of that precise science. 



For a long time heat was practically an independent 

 subject. Heat was regarded as a substance, something 

 locked up among the interstices of the particles from which 

 matter is constructed. There was no fundamental relation 

 existing between this and mechanics or other branches of 

 physics. But the work of Rum ford, Mayer, Joule, and 

 Helmholtz showed that this view of heat was incorrect. 

 According to the new theory, heat is a form of energy and 

 can be measured and stated in terms of energy units. Then 

 and only then was the way open for the acceptance of the 

 doctrine of the conservation of energy, and the extension of 

 the laws of mechanics to this subject. This is such an import- 

 ant step that I wish to explain it clearly. The fundamental 

 concepts and the laws connecting force, motion, and energy 

 were developed as applying to ordinary bodies and to motions 

 that we can perceive. They were applied to a falling body, 

 to the raising of weights by pulleys, to a revolving fly-wheel, 

 but now it is assumed that these laws can be applied to a 

 case where we do not know that we are dealing with moving 

 bodies. To apply these laws to heat is not only a radical 

 change but one which throws light upon the methods of 

 physics. In this case as a result of assuming that what 

 was true in mechanical cases would be true in all cases, 

 the way was opened for the development not only of new 

 facts but also of new and important laws of heat. One of 

 the now most important branches of this, thermodynamics, 

 owes its development to the resulting impulse given to the 

 study of heat phenomena. 



Thus we find that portions of the various branches of 

 physics may be classed as subdivisions of mechanics, but this 



