20 THE ANNUAL ADDRESS OF THE VICTORIA INSTITUTE. 



substances Avliicli when acted upon by liglit continue to shine 

 in the dark. In some cases the action ceases almost instantly 

 after the exciting light is cut off, for instance a solution of 

 the salts of quinine, Avhere the rapidity of cessation of the 

 effect is amply sufficient to tally with the rapidity of 

 cessation of visual sensation when light is cut off. 



There are various other matters connected with the 

 perception of light Avhich are of great importance to our well 

 being and to our enjoyment which I have not ventured to 

 touch upon at all. It would take a great deal too long to 

 go into two which I will only just mention. One is 

 the provision in the two eyes, and in the muscles which 

 move them, Avhicli enables us to obtain single vision not- 

 Avithstanding tliat the two eyes are at work. Nothing is 

 easier than to obtain double vision in which the images seen 

 by means of two eyes occupy different positions in the 

 field of view. There are very remarkable contrivances for 

 bringing about singleness of vision in the habitual use of 

 both eyes. 



Then, again, we do not see light merely as light, but we 

 see a great variety of colour. We can distinguish one light 

 from another light by its colour, and not by its intensity 

 only. It would take me a great deal too long to give you 

 any idea of what is known (which after all is not much) 

 as to the way in which that is effected. 



I will conclude by calling your attention to the remarkable 

 structure which is called the bacillary layer, and to what is, 

 to my mind, the overwhelming evidence it affords of design 

 in construction — design in order to bring about a pre-deter- 

 mined end. But when I say that, I do not mean at all to 

 deny that there may be, and in all probability doubtless are, 

 Avhat we are in the habit of regarding as secondary causes 

 leading up to this final end. Let me take Paley's old illus- 

 tration of the watch. If a person who had never heard of a 

 time-piece were to pick up a watch or other time-piece, and 

 Avere to notice the way the hands went round and measured 

 time, he would naturally be led to suppose that there was 

 design in the thing, and that it was constructed to mark 

 time, though he might have no notion how that Avas 

 brought about. But suppose he opened the time-piece, he 

 would see a lot of wheels and so forth, and the motion of the 

 hands which he had noticed in the first instance would be the 

 inevitable result of the motion of the wheels actuated by the 

 main-spring in the first instance ; and he might notice the 



