THE SUN. 65 



and I have cooked a beef-steak and boiled eggs hard 

 by simple exposure to the sun in a box covered with a 

 pane of window-glass, and placed in another box so 

 covered. 



(23.) From a series of experiments I made there, I 

 ascertained that the direct heat of the sun, received on a 

 a surface capable of absorbing and retaining it, is com- 

 petent to melt an inch in thickness of ice in 2 i3 m , and 

 from this I was enabled to calculate how much ice would 

 be melted per hour by the heat actually thrown on a 

 square mile exposed at noon under the equator, and the 

 result is 58,360,000 lb., or in round numbers, 26,000 

 tons, and this vast mass, has to be multiplied 50 million- 

 fold to give the effect produced on a diametral section of 

 our globe. 



(24.) And, now, let us endeavour to form some kind of 

 estimate of the temperature; that is to say, the degree or 

 intensity of the heat at the actual surface of the sun. By 

 a calculation, with which I will not trouble you, it turns 

 out to be more than 90,000 times greater than the in- 

 tensity of sunshine here on our globe at noon and under 

 the equator a far greater heat than can be produced in 

 the focus of any burning-glass ; though some have been 

 made powerful enough to melt, not only silver and gold, 

 but even platina, and, indeed, all metals which resist the 

 greatest heats that can be raised in furnaces. 



(25.) Perhaps the best way to convey some sort of 

 conception of it, will be to state the result of certain ex- 

 periments and calculations recently published ; which is 

 this that the heat thrown out FROM EVERY SQUARE YARD 



E 



