Schaw. — On the Reflection of Light. 537 



manner with a beautiful intermingling of yellow, orange, red, 

 and green., so intertwined and mingled that the effect is equally 

 beautiful and astonishing. How comes it that the reflection 

 of an object which seems uniform and dull in colour presents 

 such a varied and brilliant appearance ? The explanation I 

 take to be as follows : The cliff — although, at the distance of 

 over a mile from which it is viewed, it seems to be of a 

 uniform and somewhat dull colour — is in reality composed of 

 small pieces of clay, earth, and stone of very varied and com- 

 paratively pure colours. These are blended by distance into 

 a uniform reddish-yellow ; but each spot on the cliff, each 

 coloured piece of clay or rock or green bush, is reflected in 

 the water, and reflected not only once, but a great many 

 times, on the numerous mirrors presented by the surfaces of 

 the small ripples. This multiple reflection of each separate 

 bit of colour enlarges it, and so makes that colour evident to 

 the eye viewing the reflections from a distance, although the 

 actual spot giving off the coloured rays which are thus re- 

 peated so frequently on the water-surface is too small to be 

 detected by the eye at that distance. 



I think that wonderfully close observer of nature, the great 

 painter Turner, has, in one of his pictures of the Venice 

 Lagoon, illustrated in some degree this peculiar effect of 

 reflections from water when the surface is smooth but undu- 

 lating ; but I have never observed the effect so strikingly 

 manifested as in the reflection of that clay cliff below Mr. 

 FitzGerald's house, and I do not think that it has been 

 generally noticed or recorded by landscape-painters. 



There is to most minds a great pleasure and satisfaction 

 in tracing effects back to their causes, even although we may 

 be able only to take a few steps backwards, to detect a few of 

 the last links of the long chain of causation which has brought 

 about the result. This is all I have attempted to do on the 

 present occasion. To do more would be to go over again, very 

 imperfectly, the ground covered by the distinguished authors 

 of the latest books on light (such as those of Sir George Stokes 

 and Professor Tait), which explain the present state of our 

 knowledge of this subject, whether actual or hypothetical, and 

 also where even hypothetical knowledge ends and ignorance 

 begins. I should have to attempt to answer such questions as 

 these: — 1. What is light? 2. What is the cause of the light 

 of the sun? 3. How does this light travel from the sun to 

 the earth ? i. What are the laws of reflection and refraction 

 of light, and what are the causes of these laws? 5. What is 

 the structure of the human eye ? 6. How is the impression 

 received by the eye conveyed to me ? 7. What is life, which 

 enables me to receive the information conveyed by light to the 

 eye, and from it by nerves and brain to vie ? — and many other 



