454 [March 5, 



then immersing it one-half its depth in cold water. This was tried, 

 and found to answer perfectly, that portion of the tire which was 

 out of the water being reduced in diameter. The tire was 3 inches 

 wide, inch thick, and 4' 2" in diameter. 



As this result was curious and not generally known, I considered 

 it desirable to institute some further experiments in order to try how 

 far, by successive heatings and coolings, this change of form could be 

 augmented, and also whether the same effect could be produced on 

 other metals than wrought iron. 



Mode of carrying out the Experiments. The experiments were 

 made on cylinders of wrought iron of different dimensions, both 

 hollow and solid ; immersed, some to one-half of their depth, others 

 to two-thirds ; also on similar cylinders of cast iron, steel, zinc, tin, 

 and gun-metal. 



The specimens experimented on were all accurately turned in a 

 lathe to the required dimensions, which were carefully noted ; they 

 were then heated to a red heat in a wood-furnace used for heating 

 the tires of wheels. As soon as they had acquired the proper heat, 

 they were taken out and immersed in water to one-half or two-thirds 

 of their depth (as stated in the experiment). The temperature of 

 the water ranged from 60 to 70 Fahr. 



The specimens were allowed to remain in the water about two 

 minutes, in which time the portion in the air had lost all redness, 

 and that in the water had become sufficiently cool to handle. These 

 alternate heatings and coolings were repeated till the metal showed 

 signs of cracking or giving way. 



The dimensions were noted after every five heatings. The cir- 

 cumferences were measured in preference to the diameters, as the true 

 circular form was liable to alter. 



General Results. It will be seen by an inspection of the figures 

 that the general effect is a maximum contraction of the metal about 

 one inch above the water-line ; and that this is the same whether the 

 metal be immersed one-half or two-thirds of its depth, or whether it 

 be nine, six, or three inches deep. With wrought iron the heatings 

 and coolings could be repeated from fifteen to twenty times before 

 the metal showed any signs of separation ; but with cast iron after 

 the fifth heating the metal was cracked, and the hollow cylinder 

 separated all round just below the water-line after the second heating. 



