418 



Mr. W. Galloway on the 



[Mar. 13 y 



hole in the disk, and concentric with it, there is a thin sheet- iron pipe 

 4 inches in diameter, whose npper end almost touches the disk while 

 its lower end descends to within 4 or 5 inches of the bottom of the 

 cylinder. When the fan is made to revolve rapidly, the air passes up 

 through the central pipe with a velocity of 460 feet per minute. At 

 its upper end the spindle carries a small grooved pulley, d, which is 

 made to revolve by means of an endless cord passing round it and over 

 another large grooved driving wheel D. The lower end of the 

 cylinder rests on an iron ring screwed down to the top of the wooden 

 gallery BC, in which there is an opening corresponding to the size of 

 the cylinder. The cylinder is attached to one side of the iron ring by 

 a hinge which allows it to be folded back into the position shown in 

 fig. 4. At the other side it can be fastened by a screw in an upright 

 position as shown in the other figures. 



The gallery BO, consists of a range of wooden pipes 14 inches 

 square inside,, and, altogether, 79-J feet long. The centre of the 

 cylinder A is 5 feet from the end B, and there is a valve just below 

 the point b, by means of which the part of the gallery towards B can 

 be isolated from the remainder. The separate pipes have broad wooden 

 flanges which are put close together when they are placed so as to form 

 a gallery, but they are not fastened to each other in any way ; they rest 

 on wooden blocks a a, and any one of them can be drawn out from 

 between the two on each side without disturbing the others. This is 

 shown by the dotted lines in fig. 6. Near the end B there is a sheet- 

 iron cylinder 3 feet long by 10 inches in diameter, closed at each end, 

 and having an inlet pipe for steam at q, and an outlet pipe at t for 

 condensed water and steam. At the same end also there is a branch 

 e, f, g, leading to K, which is the horizontal part d c, of the apparatus 

 represented in fig. 1. This branch is also connected with a blowing 

 fan F, driven by a steam turbine of which I and h are the. steam and 

 exhaust pipes. The pipe bringing fire-damp from below ground,, 

 referred to in my former paper, can be made to deliver its fire-damp 

 into the air inlets of the fan in the same ' way as in the former experi- 

 ments. It will now be evident that currents of air of various qualities 

 can be made to traverse the gallery B C from B towards C. Thus, 

 if the valve s is open, while the valve s' is shut, the return air of 

 the upcast shaft passes through the apparatus and escapes at C ; but 

 if s r is open and s is shut, the return air is cut off, and by setting the 

 fan F in motion, we obtain either pure air, or air and fire-damp mixed, 

 as we may desire. In every case, also, the air passes over, and is 

 heated by, the steam cylinder jp, so that, even when return air is used, 

 the interior of the gallery CD can be kept dry. 



The interior of the cylinder A is lined with wood about "2 inch thick, 

 and its capacity is about 4*648 cubic feet. For the purpose of obtaining 

 the explosive mixture required, the cylinder E, 8 inches in diameter, 



