466 



[March 5, 



Experiment 15. A solid wrought-iron cylinder was heated to red- 

 ness and cooled by half-immersion on its side twenty times. 



The effect was of a similar nature to that of the last experiment 

 (see figs. 20 and 21). 



Fig. 20. 



Fig. 21 



One-half of full size. The dotted line indicates original figure. 



Experiment 16. A hollow cast-iron cylinder, the dimensions of 

 which were the same as those of the deep cylinder of Experiment 14, 

 was heated to redness and cooled twice by half-immersion. 



At the second cooling it fractured nearly all round, about an inch 

 below the water-line. It expanded all over, but the expansion was 

 least about an inch above the water-line, i. e. it did not contract to 

 its original dimensions. 



Experiment 1 7. A solid cast-iron cylinder, 3 inches in diameter 

 and 6 inches deep, was heated and cooled five times by half-immersion. 



At the fifth cooling it cracked across the bottom ; it also expanded 





