ADDRESS. 33 



as the time of Homer, our ancestors were blue-bliud. Thougli for my 

 part I am unable to adopt this view, it is certainly very remarkable that 

 neither the Rigveda, which consists almost entirely of hymns to heaven, 

 nor the Zendavesta, the Bible of the Parsees or fire-worshippers, nor 

 the earlier books of the Old Testament, nor the Homeric poems, ever 

 allude to the sky as blue. 



On the other hand, from the dawn of poetry, the splendours of the 

 morning and evening skies have excited the admiration of mankind. As 

 Ruskin says, in language almost as brilliant as the sky itself, the whole 

 heaven, ' from the zenith to the horizon, becomes one molten, mantlino- sea 

 of colour and fire ; every black bar turns into massy gold, eveiy ripple 

 and wave into unsullied shadowless crimson, and purple, and scarlet, and 

 colours for which there are no words in language, and no ideas in the 

 mind — things which can only be conceived while they are visible; the 

 intense hollow blue of the upper sky melting through it all, showino- here 

 deep, and pure, and lightness ; there, modulated by the filmy, formless 

 body of the transparent vapour, till it is lost imperceptibly in its crimson 

 and gold.' 



But what is the explanation of these gorgeous colors ? why is the 

 sky blue ? and why are the sunrise and sunset crimson and gold ? It 

 may be said that the air is blue, but if so how can the clouds assume 

 their varied tints ? Brucke showed that very minute particles suspended 

 in water are blue by reflected light. Tyndall has taught us that the 

 blue of the sky is due to the reflection of the blue rays by the minute 

 particles floating in the atmosphere. Now if from the white light of the 

 sun the blue rays are thus selected, those which are transmitted will be 

 yellow, orange, and red. Where the distance is short the transmitted 

 light will appear yellowish. But as the sun sinks towards the horizon 

 the atmospheric distance increases, and consequently the number of the 

 scattering particles. They weaken in succession the violet, the indigo, 

 the blue, and even disturb the proportions of green. The transmitted 

 light under such circumstances must pass from yellow throuo-h orano-e 

 to red, and thas, while Ave at noon are admiring the deep blue of the sky, 

 the same rays, robbed of their blue, are elsewhere lighting up the evenino- 

 sky with all the glories of sunset. 



Another remarkable triumph of the last half-century has been the 

 discovery of photography. At the commencement of the century Wedo-. 

 wood and Davy observed the effect produced by throwing the images of 

 objects on paper or leather prepared with nitrate of silver, but no means 

 were known by which such images could be fixed. This was first effected 

 by Niepce, but his processes were open to objections, which prevented 

 them from coming into general use, and it was not till 1839 that Daguerre 

 invented the process which was justly named after him. Very soon a 

 further improvement was eS'ected by our countryman Talbot. He not 

 only fixed his ' Talbotypes ' on paper — in itself a great convenience — but, 

 by obtaining a negative, rendered it possible to take off any number of 

 1881. D 



