434 PROCEEDINGS OF THE AMERICAN ACADEMY 



water, manufactured by the Boston Lead Company, Shaw and 

 Willard's patent. 



" The first lot was made by placing two semicylinders of pure block- 

 tin around a hollow core, or mandril, through which a current of cold 

 water could be made to run, so as to keep the tin as cool as possible. 

 The semicylinders of tin were also chilled in snow or pounded ice. 

 When placed around the core, and held closely together by tongs, 

 melted lead, at as low a temperature as it could be cast, was poured 

 around the tin, and allowed to cool, the compound cylinder being eight 

 inches long and six inches in diameter. Then, by means of a power- 

 ful hydraulic press, giving a pressure of 3,150 pounds per square inch, 

 or between four and five hundred tons upon the ram or piston, the 

 cylinder of lead and tin was forced out below, a mandril, or former, 

 keeping the inner portion of the tube open and of a uniform size. 

 When the thick cylinder was nearly driven out of its mould, the press 

 was stopped, and a new casting was made upon the remaining metal ; 

 so that continuous and perfectly united tubes of any desired length 

 were formed, and were wound up on a reel in a room below. By this 

 method, it was thought, a pipe lined with pure block-tin surrounded by 

 the more flexible lead could be produced ; but it has been found that 

 pipes made in this way charged the water which stood in them over- 

 night with lead. 



" Dr. Jackson was therefore called upon to make a series of analyses 

 of the linings of many of these tubes, and discovered that the lining 

 was composed of 22 per cent of lead and 88 per cent of tin, or an 

 alloy. He was then invited to witness the operation of making the 

 pipes, when every endeavor to prevent the penetration of the molten 

 lead into the substance of the tin proved that it was impossible, so 

 long as the molten lead was cast around the tin, — for the lead requires 

 a temperature of 612° for its fusion, and tin only 442° ; while the 

 great mass of hot lead rendered the tin almost a paste, into which the 

 lead readily penetrated. There being 170° difference between the 

 melting-points of the two metals, it was suggested that, if the lead was 

 cast first around an iron core, and, when cold enough, on withdrawing 

 the core and casting in the tin, the difficulty might be remedied. This, 

 the foreman of the works said, could be easily effected, and it was soon 

 after done with entire success ; for chemical analysis showed the tin 

 lining of such pipes to be absolutely pure tin. By this improved pro- 



