INAUGUKAL ADDRESS. 3 



years past, and are of the same type as those emitted by the radio- 

 active substances; for the extension of knowledge which has followed 

 on the discovery of the latter has been so great that previous investi- 

 gations can rank only as an introduction to the new science. Never- 

 theless, novel as the new- radiations are in their origin and properties, 

 it i.^ important to observe that the recent investigations can be looked 

 ujion as the latest stage of a long inquiry of first importance, relating 

 to radiation in general. For ages men have asked themselves, " What 

 is light? " When the ancient writer recorded as one of the great acts 

 of creation the command of God, " Let there be light !" he testified 

 truly of its importance to mankind, and bore witness to the extent to 

 which the seers of his day had grasped that importance. When men 

 bowed to sun and moon and stars, they did but recognise their debt to 

 the radiation on which their whole lives seemed to depend. And 

 though we can now look past these creatures of light and heat, yet 

 still we recognise their vast importance in the universal scheme. Not 

 only are they necessaiy to our life upon the earth, but they alone 

 bring us intelligence from the infinities of space, and help our thoughts 

 to rise from the earth and stretch themselves to worthier and greater 

 comprehensions. It is no matter of surprise that the study of the 

 character and properties of radiation has at all times filled the 

 thoughts of men. 



There are two sides of this study to which I would particularly 

 call your attention. We examine the properties of radiation in order 

 to discover on the one hand the nature of radiation itself, on the other 

 the nature and constitution of the atoms or molecules which emit it. 

 For such information as we can obtain of the nature of atoms is of the 

 utmost value since it is one of the main purposes of science, having 

 once recognised the atomic composition of all material substances, to 

 seek how to account for the properties of bodies in bulk from a know- 

 ledge of the properties of the atoms of which those bodies are com- 

 ]iosed. We, therefore, try to judge the atom by that radiation which 

 pi'oceeds from it. We can never hope to see an atom in the sense in 

 which we see objects generally; we must form our estimates by in- 

 direct means. Yet the direct and the indirect are not so entirely 

 different as might at first appear. We draw our conclusions as to the 

 form, colour, and position of the objects which we see in this room by 

 the aid of the radiation emitted by the artificial light. The radiation 

 is reflected, scattered, and modified by the surfaces on which it falls ; 

 and our seeing is really no more than the perception and interpretation 

 of these effects. In fact, the objects in the room are emitting radia- 

 tion, boiTowed, it is true, and thereby we judge them. In this case 



