1863.] 



461 



one-half the amount. They were both turned up into the form of 

 an arc, had thickened on their upper edges, and increased '1 inch in 

 thickness where the contractions on the ends took place (see figs. 

 11 and 12). 



Fig. 11. 



Fig. 12. 



One-fourth of full size. 



Experiment 8. Two hollow wrought-iron cylinders, 9 inches 

 deep and 12 inches in diameter, were heated and cooled, one by 

 simple exposure to air (fifteen times), and the other by total 

 immersion in water (ten times). No alteration occurred in the 

 form of either*. 



* The cylinder which was cooled in air weighed, before the experiment, 49 Ibs. 

 14-5 ozs., and after the experiment 49 Ibs. 11 ozs., showing a loss by scaling of 

 3-5 ozs. 



During the progress of the experiment, however, it was frequently weighed, and 

 was found each time to have increased in weight up to the tenth heating, at which 



VOL. XII. 2 L 



