Section A. 



(ASTRONOMY, MATHEMATICS, PHYSICS, AND MECHANICS.) 

 President op the Section — Professor Lyle, M.A. 



ADDEESS BY THE PEESIDENT. 



Advances in Physical Science and. its Application. 

 Plates I. and II. 



In opening the proceedings for which we are assembled, I wish 

 to thank the Australasian Association for the Advancement of 

 Science for the honour it has done me in electing me President 

 of Section A, which includes astronomy, mathematics, and 

 physics. I sincerely wish that the post was filled by some one 

 better qualified to perform the duties belonging to it, though at 

 the same time I must admit that I am very proud of the 

 distinction. 



I propose as my task to-day to review briefly, and in some 

 cases explain in as simple terms as I can, a few of the wonderful 

 advances that have been made of late in physical science and 

 its applications. 



The most tremendous of the many achievements of the 

 latter half of the nineteenth century is, without doubt, the 

 development of our knowledge of the properties of the ether, of 

 the ethereal theory of electricity, and the absolute proof that 

 light and electro-magnetic radiation are one and the same 

 phenomenon. 



The idea that something must of necessity fill space is by 

 no means new. The unthinkableness of the " action at a 

 distance ' ' of one body on another across empty space with 

 nothing between them as a means of communication was seen 

 by Newton. He could not understand how the sun and earth 

 mutually attracted each other by gravitation unless there was 

 some medium between them by which the action was commu- 

 nicated. 



If you apply yourselves seriously to think of the matter, you 

 will see that there can be only two possible modes of communi- 



