4 PHYSICAL SCIENCE 



The domain of physical science, concerning which I have the 

 honor to address you to-day, presents peculiar and peculiarly for- 

 midable difficulties in the way of a summary review. While we may 

 not be disposed to limit the wide range of inclusion specified by our 

 programme, we must at once disclaim any attempt to speak author- 

 itatively with respect to most of its details. There is, in fact, such 

 a vast array of knowledge now comprehended under any one of the 

 six Departments of our Division, that the boldest author must hesi- 

 tate to enter on a limited discussion with respect to any of them. 

 But if it is thus difficult to consider any department of physical 

 science, it appears incomparably more difficult to contemplate all 

 of them in the bewildering complexity of their interrelations and 

 in the bewildering diversity of their subject-matter. What, for 

 example, could seem more appalling to the average man of science 

 than the duty of explaining the connections of archeology and astro- 

 physics, or those of ecology and electrons? 



Happily, however, the managers of the Congress have provided 

 an adequate division of labor, whereby the technical details of the 

 various Departments are allotted to experts, giving thus to a divis- 

 ional speaker a degree of freedom with respect to depth in some 

 way commensurate with the breadth of his task. Presuming, there- 

 fore, that I may deal only with the broader outlines and salient 

 features of the subject, I invite your attention to a summary view 

 of the present status and the apparent trend of physical science. 



Whatever may be affirmed with respect to science in general, 

 there appears to be no doubt that all of the physical sciences are 

 characterized by three remarkable unities, a unity of origin, a 

 unity of growth, and a unity of purpose. Physical science originates 

 in observation and experiment; it rises from the fact-gathering 

 stage of unrelated qualities to the higher plane of related quantities, 

 and passes thence on to the realm of correlation, computation, and 

 prediction under theory ; and its purpose is to interpret in consistent 

 and verifiable terms the universe, of which we form a part. The re- 

 cognition of these unities is of prime importance ; for it helps us to 

 understand and to anticipate a great diversity of perfection amongst 

 the different branches of science, and hence leads us to appreciate the 

 desirability of hearty cooperation on the part of scientific workers in 

 order that progress may be ever positive towards the common goal. 



Glancing rapidly seriatim at the different departments of physical 

 science as specified by our programme, we come first to a consider- 

 ation of formal physics, and we may most quickly orient ourselves 

 aright in this department by trying to state in what respects the 

 physics of to-day differs from the physics of a hundred years ago. 



In spite of the extraordinary perfection of the work of Lagrange, 

 Laplace, Fourier, Young, Fresnel, Poisson, Green, Gauss, and others 



