402 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



of a piston playing in it, to a certain point, at which its strength 

 had become sufficient to resist further expansion. The inner 

 layers of the tube were first expanded, and the process was con- 

 tinued until the outside layer could exert its full power in resist- 

 ing the expansive strain. A cast-iron gun begins to crack in the 

 centre before it can expand sufficiently to cause the external 

 layer to operate. Steel may be six times stronger than cast-iron, 

 but when this principle is taken into consideration, the steel 

 tube of but one-sixth the thickness, will be stronger than the 

 cast iron tube. A tube can be made very much stronger by 

 winding it with wire, so stretched as to operate through its 

 whole length. This wire may be made square or flat. Jacob 

 Perkins made an extremely strong vessel by taking half a dozen 

 vessels so fitted that each had to be heated before the inner ones 

 could be put in. 



Mr. Stetson said that the strain upon the end of the gun, 

 which is not assisted in this way, must not be forgotten. 



The same subject, " Steel guns, and the preparation of the 

 material," was continued. 



Adjourned until Thursday, July 11th. 



American Institute, Pol 

 Mr. Tillman was called to the chair 



YTECHNic Association, ) 

 July 11, 1861. I 



alloy of cadmium. 



Mr. Churchill said that Dr. Wood had recently patented an 

 allo}^ of cadmium, fusible at low temperatures, and therefore 

 capable of being used for soldering under hot water. His 

 patent, however, appears to be too broad, for as long ago as 

 1851, a formula was published for an alloy of cadmium with tin, 

 which was especially recommended for dentists' use. 



•The Chairman stated that, acco|;ding to Silliman's Journal, Dr. 

 "Wood has produced an alloy melting at a lower temperature than 

 any other heretofore made. 



Prof, Seely said that the formula referred to was not properly 

 for an alloy .but for an amalgam ; two parts of tin to one part of 

 cadmium, to be dissolved in mercury. He should not, therefore, 

 consider the criticism of Mr. Churchill as just. 



Mr. Churchill said that the alloy was first to be made, and 



