MECHANICS AND USEFUL ARTS. 89 



previous to entering the tube of the boiler. In this box is a slanting 

 door, for the purpose of cleaning the tubes, as well as for safety in 

 case of explosion, when it is forced open, thereby preventing injury to 

 the flues. Beneath this first box is another box or burner, made of thin 

 sheet-iron, having an opening nine inches by three fourths of an inch, 

 through which atmospheric air in thin sheets is admitted to consume 

 the gases, the top being placed on a level with that of the tube. The 

 gases thus pass from the first box to the entrance of the boiler-tube, 

 where the air is admitted through the burner or burners, and the 

 whole is igniicd by means of a little fire placed at the entrance, and 

 inside the door, care being taken to prepare this fire a short time be- 

 fore bringing down the gnses. Combustion then takes place in and 

 through the tube, a side flue, and back along the flue to the stack. 

 Holes are left in the brick-work so that the combustion of the gas can 

 be seen, and the gases are easily shut off when it is desirable. 



HYDROSTATIC BLOWING-PIPE. 



THE Scientific American, for March 2, describes a " hydrostatic 

 blowing-pipe " for producing the blast of air required in smelting and 

 heating operations. It consists generally of a wheel or drum placed 

 in a cistern or flume, with air-cells, a reservoir for air, and valves be- 

 tween the two heads of the drum. The air-cells on the periphery of 

 the drum are so many boxes with valves on the bottom. As the 

 wheel is turned, these boxes are successively plunged into the w r ater 

 while in an inverted position, and the air with which they were filled 

 when entering it is forced through their valves into the drum of the 

 wheel, by the pressure of the waler from below, the strength of the 

 blast being thus determined by the depth of immersion. Water is let 

 into the flume until about one third of the diameter of the wheel is 

 immersed. Where water-power is abundant, paddles or buckets may 

 be placed on the wheels, and a current of about four miles an hour 

 given to the water, which will turn the wheel and produce the blast. 

 Where economy of power is desired, the blowing-wheel may be sus- 

 pended in a cistern or circular trough, and turned by steam or any 

 other power. The claims of this machine are founded upon its econo- 

 my and simplicity. 



IMPROVEMENTS IN FORGING AND IN WELDING IRON. 



MR. NASMYTH described to the British Association, at Edinburgh, 

 an improvement of his, which tends to increase the certainty of the 

 production of perfectly sound and solid cylindrical forgings, especially 

 those of large size, such as shafts, axles, and the like. In the com- 

 mon method, by which the metal is placed upon a flat anvil, the effect 

 of the hammer is to spread the metal out in one direction, and this 

 must be corrected by turning it round, so that each successive blow 

 may correct the spreading caused by the previous one. This causes a 

 fretting or mincing of the centre part of the metal of the shaft or other 

 forging, resulting in a separation of the metal throughout the entire 



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