RADIANT HEAT AND ITS RELATIONS 101 



define the term use. If you meant to ask whether those 

 dark rays which clear away the Alpine snows will ever be 

 applied to the roasting of turkeys, or the driving of steam- 

 engines while affirming their power to do both, I would 

 frankly confess that they are not at present capable of 

 competing profitably with coal in these particulars. Still 

 they may have great uses unknown to me; and, when our 

 coal-fields are exhausted, it is possible that a more ethe- 

 real race than we are may cook their victuals, and perform 

 their work, in this transcendental way. But is it neces- 

 sary that the student of science should have his labors 

 tested by their possible practical applications ? What is 

 the practical value of Homer's Iliad? You smile, and 

 possibly think that Homer's Iliad is good as a means of 

 culture. There's the rub. v The people who demand of sci- 

 ence practical uses, forget, or do not know, that it also is 

 great as a means of culture that the knowledge of this 

 wonderful universe is a thing profitable in itself, and 

 requiring no practical application to justify its pursuit. 



But, while the student of Nature distinctly refuses to 

 have his labors judged by their practical issues, unless the 

 term practical be made to include mental as well as ma-' 

 terial good, he knows full well that the greatest practical 

 triumphs have been episodes in the search after pure natu- 

 ral truth. The electric telegraph is the standing wonder 

 of this age, and the men whose scientific knowledge, and 

 mechanical skill, have made the telegraph what it is, are 

 deserving of all honor. In fact, they have had their re- 

 ward, both in reputation and in those more substantial 

 benefits which the direct service of the public always car- 

 ries in its train. But who, I would ask, put the soul into 

 this telegraphic body? Who snatched from heaven the 



