Wrought Iron when Heated and then Cooled. 



393 



of the Royal Carriage Department, to whom also I am indebted for 

 the accompanying diagrams. The exact dimensions of each specimen 

 before and after heating are given in a tabulated form at the end of 

 the paper, to facilitate comparison. 



In figs. 22 and 23 the changes in form of the 9" cylinders (one 

 immersed one-half, the other two-thirds its depth) are shown in 

 section after every five heatings (half the full size). 



Experiment. 1 — A 4 ft. 2 in. hoop-tire of 3 inches breadth and -f ths 

 inch in thickness (fig. 1) was heated and cooled by being immersed 

 to half its depth in cold water five times, by which the effect shown 

 in fig. 2 was produced. 



Fig. 1 



Fig. 2. 



One-eighteenth of full size. 



The upper edge, or that cooled in air, had contracted 8 inches, or 

 -^-th its entire length, and slightly increased in thickness ; while the 

 lower edge, cooled in water, had expanded '875 inch, making a dif- 

 ference between the two circumferences of 8'8 75 inches. The breadth 

 remained unaltered (3 inches), and kept perfectly straight. 



Fig. 3. 



Section showing the amount of contraction. One-half the full size. The dotted 

 lines show the original form. 



The quality of the iron was afterwards tested by pieces taken from 

 Phil. Mag. S. 4. Vol. 26. No. 176. Nov. 1863. 2 D 



