640 Transactions of the American Institute, 



weight of the breech-piece is 15 cwt. The diameter of the bore is 

 fourteen inches, and the total length of the barrel is seventeen and 

 a half feet. It is rifled, and contains forty grooves one-fifteenth of 

 an inch deep. It carries a solid shot weighing 1,100 Prussian 

 pounds, or a steel shell weighing 981 pounds. Weight of powder 

 charge, from 100 to 120 pounds. The gun-can-iage weighs fifteen 

 tons, and will turn upon a turn-table now in the course of construc- 

 tion, the total weight of which will be twenty-five tons. This 

 can be worked by two men. The cylindrical tube forming the 

 piece is made of a solid forging of steel. Three superposed rings 

 or cylinders of diflferent lengths, weighing thirty tons, are shrunk 

 upon the central tube, which weighs twenty tons. To manufac- 

 ture this gun, work was carried on night and day for sixteen 

 months. It was brought to Paris on a railway truck made at the 

 same works specially for this purpose. The price of the piece, 

 including the carriage, is 145,000 Prussian thalers, or $105,270. 



PUEE DISTILLED WATER. 



Stas, in his researches regarding atomic weights, to obtain per- 

 fectly pure water, destroyed the volatile organic matter which is 

 liable to become fixed, by passing the vapor of water slowly 

 through a long tube of copper filled with roasted copper turnings; 

 the water condensed from this vapor was redistilled in a platinum 

 refrigerator. However, finding this process too slow, he devised a 

 quicker method, by which a person may produce water in which it 

 is impossible to discover the slightest trace of organic matter. He 

 mixed pulverized manganate of potassium with the smallest quan- 

 tity of water necessary to dissolve the whole, and lets it rest in a 

 closed vessel. Four or five per cent of the solution, which becomes 

 of a clear and deep green color, is added to the water to be dis- 

 tilled. After the mixture has been left for twenty-four hours, he 

 puts in the retort with it a litre or two of concentrated solution of 

 manganate of potassium, and an equal volume of a solution of 

 hydrate of potassium, sufliciently concentrated to give stability to 

 the salt, and to enable its dilute solution to resist for a longer time 

 the action of heat without decomposing. The retort is filled to 

 about eight-tenths full of the prepared water, and the whole is dis- 

 tilled in the usual way. When rain water is used, the ammonia is 

 not removed by this process, and it is essential to redistil it, with 

 some thousandths of mono-sodic or mono-potassic sulphate. 



