LAUGEL'S PROBLEMS OF NATURE AND LIFE. 321 



ing championship. Even in the case of heat as a force 

 this comment has its application. This great power, 

 so essential to life and all existence on earth, is now 

 deemed to be a mode of motion of matter itself ; and 

 its variations to depend on interchanges of such atomic 

 motions, tending to equalise their degree, or cause 

 their conversion into mechanical or other kinds of 

 force. The main fountain of heat to us, as well as of 

 light, is the sun. This great body projects, through 

 the ether of intervening space, waves or impulses so 

 variously and wonderfully propertied as to produce, on 

 reaching the earth, those several effects of light, heat, 

 and chemical action of which the solar spectrum is the 

 simple but sublime interpreter. To the sun, then, we 

 must look for that astonishing initial force, whatever it 

 be, which from age to age combines and emits those 

 complex undulations of which heat and light are the 

 exponents to us on earth, while they alike pervade 

 every part of the solar system. We may admit that 

 heat, as expressed by temperature in the grosser forms 

 of matter, is simply due to intestine movements of 

 their particles ; but we cannot exclude the sun as the 

 present primary source of that power which these 

 motions distribute and equalise. The discoveries of 

 Tyndall show by what subtle molecular adjustments 

 the heat thus received is prevented from freely radia- 

 ting back into space. The question whether the sun 

 loses by this unceasing emission of power for we are 

 not authorised to call it substance and how this loss, 

 if real, is repaired, have been subjected to various 

 recent hypotheses, but without any certain or even 



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