ON THE AGE OF THE SUN'S HEAT. 361 



water. From this it would follow with certainty 

 that his temperature sinks 100 Cent, in some time 

 from 700 years to 700,000 years. 



What then are we to think of such geological 

 estimates as 300,000,000 years for the " denudation 

 of the Weald " ? Whether is it more probable 

 that the physical conditions of the sun's matter 

 differ 1,000 times more than dynamics compel us 

 to suppose they differ from those of matter in 

 our laboratories ; or that a stormy sea, with pos- 

 sibly channel tides of extreme violence, should 

 encroach on a chalk cliff 1,000 times more rapidly 

 than Mr. Darwin's estimate of one inch per 

 century ? 



PART II. 



ON THE SUN'S PRESENT TEMPERATURE. 



At his surface the sun's temperature cannot, as 

 we have many reasons for believing, be incompar- 

 ibly higher than temperatures attainable artifically 

 in our terrestrial laboratories. 



Among other reasons it may be mentioned that 



