370 PROCEEDINGS OP THE AMERICAN ACADEMY 



Alvan Clark, Esq., of Cambridge, in Class I. Section 2. 



Right Rev. John B. Fitzpatrick, of Boston, in Class III. 

 Section 4. 



Sir William Fairbairn, of Manchester, England, was chosen 

 a Foreign Honorary Member, in Class I. Section 4j in place of 

 the late Robert Stephenson. 



Prof. Treadwell, in a communication upon improvements in 

 heavy ordnance, took occasion to criticise a recent work upon 

 this subject by Captain Rodman, U. S. A. 



The work in question is contained in a series of Reports made by 

 Captain Rodman, of his experiments, performed, thi'ough a number of 

 years, and at a very great expense to the government, and now printed 

 in a very costly form, but not pubUshed, in the usual sense of that word. 

 The experiments had for their ultimate object the improvement of 

 cast-iron ordnance, and more especially to prove the value of a method, 

 devised by Captain Rodman, of cooling the gun from its fluid state. 

 To accomplish this, he restores the old method of casting the gun upon 

 a core, and passes through the axis of this core a stream of cold water. 

 The purpose of this is to produce a more perfect equilibrium of the 

 particles of iron than they possess when the cooling is performed from 

 the outside surface, as is the case when guns are cast solid. This 

 seems to be a good method for casting large guns, and the few experi- 

 ments that have been made upon proving, to extremity, guns cast in 

 this way, show in its favor. He pi'oduces, after all, but a cast-iron 

 gun, and the labors of others, upon other materials, have established 

 the fact that cast-iron guns and round shot are soon to give place to 

 another generation, formed of a different material and upon an entirely 

 different plan. But of this I shall speak hereafter. 



The first question now is, whether Captain Rodman's experiments, 

 and the deductions drawn from them, are trustworthy. Now, the 

 whole superstructure which he lays out, and proposes to raise, depends 

 upon an instrument which he has constructed for determining, as he 

 supposes, the actual force of the fluid produced by fired gunpowder 

 under almost all possible circumstances, and the power of cast-iron 

 guns to resist the force thus created without being destroyed by it. 

 This instrument is at once the compass, quadrant, and chronometer by 

 which he is guided in his voyage of discovery. It is described 

 particularly at pages 174 and 175, with a good plate annexed. Plates 



