370 POPULAR LECTURES AND ADDRESSES. 



greater in January than in July ; and neither at 

 the equator nor in the northern or southern hemi- 

 spheres has this difference been discovered by 

 experience or general observation of any kind. 

 But as for the mere age of the sun, irrespective 

 of the question of uniformity, we have proof of 

 something vastly more than three thousand years 

 in geological history, with its irrefragable evidence 

 of continuity of life on the earth in time past for 

 tens of thousands, and probably for millions of 

 years. 



Here, then, we have a splendid subject for 

 contemplation and research in Natural Philosophy 

 or Physics the science of dead matter. The sun, 

 a mere piece of matter of the moderate dimensions 

 which we know it to have, bounded all round by 

 cold ether, 1 has been doing work at the rate of four 



1 The sun warms and lights the earth by wave motion, excited in 

 virtue of his white-hot temperature, and transmitted through a 

 material commonly called the luminiferous ether, which fills all 

 space as far as the remotest star, and has the property of trans- 

 mitting radiant heat (or light) without itself becoming heated. I 

 feel that I have a right to drop the adjective luminiferous, because 

 the medium, far above the earth's surface, through which we receive 

 sun-heat (or light), and through which the planets move, was called 



