88 RADIANT HEAT. 



similar to light. It is true that we appear to be tending 

 towards some point of proof on this problem ; but we 

 are not in a position to declare them to be forms of one 

 common power, or " particular solutions of one great 

 physical equation,"* In many instances it would cer- 

 tainly appear that one of these forces was directly neces- 

 sary to the production of the other ; but we have also 

 numerous examples in which they do not stand in any 

 such correlation. 



We learn, from the scientific facts which we have been 

 discussing, a few of the secrets of natural magic. In 

 their relations to heat, every flower, which adds to the 

 adornment of the wilds of nature or the carefully -tended 

 garden of the florist, possesses a power peculiar to itself ; 

 and, as we have before indicated, the 



" Naiad-like lily of the vale," 

 and, 



" The pied wind-flowers, and the tulip tall, 



And narcissi, the fairest among them all," 



are, by their different colours, prevented from ever 

 having the same temperatures under the same 

 sunshine. 



Every plant bears within itself the measure of the 

 heat which is necessary for its well-being, and is endued 

 with functions which mutely determine the relative 

 amount of dew which shall wet its coloured leaves. 

 Some of the terrestrial phenomena of this remarkable 

 principle will still further illustrate the title of this 

 volume. 



To commence with the most familiar illustrations, let 

 us consider the consequences of change of temperature. 



* Dr. Robinson, of Armagh, in his Memoir On the Effects of 

 Heat in lessening the Affinities of the Elements of Water. Transac- 

 tions of the Royal Irish Academy, vol. xxi. part 2. 



