PHYSICS 71 



spicuously. For the important results of this work as well 

 as its unusually rapid development have been due to the fact 

 that physicists and chemists have worked together. I may 

 illustrate this further by cases drawn from but one side. 

 Much of the work that has been done in determining the 

 absolute mass of an atom has been done by physicists. We 

 find the head of the Cavendish Physical Laboratory, Sir. J. 

 J. Thomson, working out the structure of an atom and trying 

 to give an explanation of what has been called chemical 

 affinity. The physicist, Rutherford, has recently not only 

 devised a way for counting and weighing single atoms of 

 helium, but in actually isolating them. It certainly does not 

 require much imagination to predict that some day the attitude 

 of the chemist and that of the physicist will become identical. 



Turning to the other physical sciences we find that these 

 are in part at least applications of those fundamental laws 

 of mechanics. When mechanics is applied to the outer uni- 

 verse we have astronomy. The well known great accuracy 

 of astronomical calculations, for example the exactness with 

 which an eclipse can be predicted, is only another example 

 of the precise character of this subject mechanics. The 

 application of mechanics to the movements of the air and 

 moisture is called meteorology. This is not a precise science 

 for the simple reason that it has not yet been reduced to simple 

 mechanical principles. Geology may be said to be an appli- 

 cation of mechanics and heat to the study of the earth's crust. 



The subject of physics proper is more limited than it yet 

 appears. Today, owing largely to the growth of the en- 

 gineering sciences, its scope is more restricted than ever 

 before. The facts seem to be that whenever some special 

 application of physics has been of sufficient importance to 

 warrant a group of men giving their whole time to that 

 subdivision, then this branch is dignified by a name and is 

 ranked as one of the sciences. Thus in recent years has 

 developed the subject of electrical engineering. 



