ASTRONOMY AS A SCIENCE. THE SUN. 121 



tion, emitting the same light, and even yielding in some 

 instances a certain evidence of the same material con- 

 stitution. 1 



Becurring, however, to the sun, as one more special 

 illustration of modern astronomy, we must look again 

 as a part of this science to the still unexhausted wonders 

 of the solar spectrum. This spectrum, formerly seen in 

 its prismatic colours only, has now become the expo- 

 nent of invisible rays, stretching far beyond its visible 

 extremities ; propertied as heat at one extremity, and 

 with those specific chemical actions at the other, which 

 have given a new and beautiful art to mankind. The 

 undulations conveying (or forming) the three powers 

 thus blended in a single beam have specific relations to 

 the different forms of matter on earth, such in kind and 

 so essential that life and organisation would cease to 

 exist deprived of their influence. Science is every day 

 disclosing new and unexpected relations to this effect ; 

 while the powerful prismatic spectroscopes now brought 

 into use are analysing, still more minutely, and under 

 varying conditions of heat and density in the gases 

 evolving them, those spectrum lines of different ele- 

 ments, the relations of which have given us such 

 unlocked for access to the matter of the sun itself. 



This unceasing derivation of light and heat, and 

 perhaps other powers, from the sun a derivation not 

 limited to our planet, a speck in the firmament, but 



1 Milton, in the phrases of his noble poetry, might almost be said to 

 predicate those discoveries of our own day. In the third book of l Para- 

 dise Lost ' he speaks of the sun's magnetic beam, and in the same passage 

 of the arch-chemic sun. A certain sort of inspiration and vaticination of 

 the future often seems to enter into the higher poetry of each age. 



