PHYSICAL SCIENCE. 29 



light discoveries which have given or added lustre to the 

 names of Young, Malus, Fresnel, Arago, Brewster, Wheat- 

 stone, Hamilton, and others scarcely less eminent in this 

 enquiry. 



A word or two we must add here as to one relation 

 simple in fact, but not familiar to thought which light 

 establishes between man and the universe around. The total 

 science of astronomy belongs in origin to this element alone. 

 Extinguish those vivid points or bright surfaces of light 

 which give splendour to the midnight sky; deprive the 

 astronomer of the feebler rays and fainter gleams which stars 

 and nebulae, invisible to the eye, bring before his telescope ; 

 and you annihilate at once that science which can predict 

 eclipses centuries beforehand; determine the orbits and 

 return of comets ; measure the distances of the fixed stars, 

 and the motion of our own sun and solar system in the uni- 

 verse of space ; and penetrate into systems of worlds beyond, 

 where relative degrees of light become the solitary evidence 

 of form and distance. Nowhere are these relations of astro- 

 nomy to light so well illustrated as in Arago's ( Analysis of the 

 Life and Labours of the elder Herschel,' recently republished 

 in the collection of his works. 



Other relations still remain to be noticed here. The 

 phenomena of polarisation, as discovered on the earth, have 

 carried our knowledge nearer to the fountains of this great 

 elemental power ; confirming Sir W. Herschel's opinion that 

 light issues, not from the body of the sun, but from a lumi- 

 nous envelope, or photosphere around it. Yet further, the 

 astronomer is able to show, by placing a prism before the 

 object-glass of his telescope, that the light from the fixed 

 stars is submitted to the same refraction, evolves the same 

 colours, and possesses the same velocity as that of the sun, 

 thus more explicitly denoting the sun itself as a simple star 

 in the vast sidereal system. Even the new science of photo- 



