I. TO HAMPSTEAD. 9 



nomenon of light, though it is one of the 

 most wonderful that nature exhibits to our 

 view, and one which excites the greatest 

 surprise and gratitude in the mind habituated 

 to observe it with attention. 



It would appear that the rays of light are 

 transmitted to us through the medium of a 



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fluid, which occupies the space between our 

 eye and the object we are viewing. 



But of what nature is that fluid ? Does it 

 flow directly from the sun ? or is it diffused 

 through the immensity of space, and 

 brought into action bv the rotatory motion 



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of the sun, or by any other cause ? We 

 cannot reply to these questions, my beloved 

 children, without involving ourselves in 

 vague theories and conjectures. All that we 

 certainly know, is, that the sun appears to 

 be the focus of light ; that his rays, wtich 

 opticians have succeeded in separating, or 

 decomposing, contain the different primi- 

 tive colors ; and that, in short, the motion 

 of light is so rapid, that it moves or proceeds 



at 



