in Fluids. 387 



the Heat, all the water In the tube to within one quarter 

 of" an inch of the ice may be brought into the most vio- 

 lent ebullition before the ice will begin to be melted, and 

 at last will appear to boil even at the very surface of the 

 ice. 



§ 3. The radiant Heat from a red-hot Iron Bullet does not 

 appear to be able to make its Way downwards through 

 liquid Water ^ nor through melted Tallow^ nor melted Wax. 



1st Experiment. — A very small mercurial thermom- 

 eter, with a naked globular bulb, was laid down in an 

 horizontal position on two small projections of wax, in 

 the bottom of a shallow wooden dish, in such a manner 

 that, the engraved scale of the thermometer lying upper- 

 most, the height of the mercury in its tube could be 

 observed. This being done, I poured cold water into 

 the dish till it stood at the height of about \ of an inch 

 above the bulb of the thermometer, and then presented 

 to the thermometer an iron bullet about i|- inches in di- 

 ameter, red-hot, which I held (by means of a fit handle) 

 directly over its bulb at the distance of about an inch. 



The thermometer seemed to take very little notice of 

 the vicinity of the red-hot iron. 



When its bulb was covered with oil the result of the 

 experiment was much the'same, but when it was exposed 

 naked, or uncovered by a liquid, to the rays from the 

 hot iron, it appeared to acquire Heat very rapidly. But 

 the two following experiments were still more decisive 

 and satisfactory. 



2d Experiment. — A shallow earthen dish, about 3 

 inches deep and 12 inches in diameter at its brim, was 

 filled with water, and, being exposed in a cold room in 



