1863.] 



457 



condition had remained unchanged, the specific gravity had not 

 altered appreciably, and there appeared to be no deterioration in any 

 part of it. 



Experiment 2. Two hollow cylinders of wrought iron, 12 inches 

 diameter and ^ inch thick each, and respectively 9 inches and 6 inches 

 deep, were heated to redness, and cooled by half- immersion in cold 

 water twenty times; for effects see figs. 4 and 5. 



Fig. 4. 



Fig. 5. 



One-eighth of full size. 



The 9-inch cylinder did riot alter on the upper edge, cooled in air ; 

 but the lower edge, cooled in water, contracted *6 inch, and the cir- 

 cumference, at about one inch above the water-line, was reduced 5-5 

 inches ; the internal surface had increased in depth *35 inch. 



The small cylinder diminished * 7 inch on the upper edge, increased 

 3 inch on the lower edge, and contracted 5 "25 inches at about 

 1 inch above the water-line; the internal surface had increased in 

 depth *3 inch. 



Experiment 3. A cylinder of very thin wrought iron, so thin that 



