178 ANNUAL OF SCIENTIFIC DISCOVERY. 



alloys, the metals unite in definite proportions at different temperatures, and 

 that in the cooling of brass castings the particles arrange themselves in a 

 manner not yet well understood. A number of small bronze guns were cast, 

 and bars were cut from different parts of them and tested. The material was 

 the same in all cases, eight parts of copper 'and one of tin; they were all 

 treated alike, and cast from the same molten mass. The samples of bars 

 tested gave an extraordinary variety of results. A bar cut from one part of 

 a gun exhibited a tenacity of 100, while a bar cut from another part of it 

 exhibited a tenacity of 236 ; and the difference in the density of different 

 parts of the same casting was also remarkable, being equal to 34 Ibs. in a cubic 

 loot, thus showing, we conceive, that the metals of alloys do unite in different 

 proportions at different degrees of temperature. Three howitzers were cast 

 from the same molten mass, poured at different temperatures into separate 

 moulds. The first was poured at a very high heat into its mould ; the metal of 

 the second was kept fifteen minutes in the ladle before it was poured in, and 

 the third kept fifteen minutes longer still. All the attending circumstances, 

 excepting the temperature of the alloy when poured into the mould, were equal. 

 The liquid metal of the first and greatest heat sank gradually down into the 

 mould for a few minutes after casting, and receded about an inch and a half 

 below its original height ; soon after this it boiled at the surface as if gas were 

 escaping, and fluid portions of the alloy arose and overflowed the top of the 

 mould. The exuded metal congealed like lava, was of a dirty white appear- 

 ance, and contained more tin than the mass of the casting. "When cold, the 

 casting was found to be an inch longer than the mould, and it was filled with 

 minute vesicular cavities. The bars cut from it and tested, were very low in 

 density and inferior in tenacity. The second howitzer cast fifteen minutes 

 later at a lower temperature was shorter, when cold, than the mould, by nearly 

 two inches. The third, cast at a still lower temperature, was, when cold, 

 three inches shorter than the mould. The density of the bars cut from these 

 three howitzers was greatest in the one cast at the lowest temperature, and 

 as the tenacity follows the same law, it appears that casting brass at a high 

 temperature is injurious to the quality of the casting the difference in the 

 tenacity of the three castings being as 3 to 1. In reference to this point the 

 report of Major "Wade says : " The division of copper and tin into two or more 

 separate alloys probably occurs at some definite temperatures ; one division 

 may occur in the liquid mass, and another after the temperature falls below 

 the melting of copper, and the latter probably occurs in ah 1 large castings, for 

 on a close examination of any gun casting, some traces of this whitish alloy 

 will be found in some parts of it. That such a division may occur in the liquid 

 mass, appears evidenl from the fact, that a portion of the liquid bronze will 

 pass through a porous vessel as through a sieve, while another portion will 

 remain within the vessel. The former is the more fusible alloy, the latter 

 the less fusible, and forms the mass of gun castings. It thus appears that 

 we may sift the more fusible alloy while both are liquid." 



It was also discovered, in the course of these experiments with alloys, 

 that small bars of bronze cast of the same metal as the cannon, were vastly 

 stronger than the cannon. This is attributed to the rapidity with which they 



