LOCOMOTIVE ENGINE. 



419 



FIG. 8. 



GAUGES. L L, (Plates XC. and XCII.,) is a glass gauge for show- 

 ing the height of the water in the boiler ; it is shewn detached in 

 fig. 8, which is a section through the centre of it to a scale of 2% 

 inches to a foot, or three times the size of the engraving. The 

 gauge consists of a strong glass tube, A, fig. 8, about three quarters 

 of an inch diameter outside, fitted into a brass socket, B B, at top 

 and bottom, the joints being made steam-tight by hemp packing, 

 put round the glass, and compressed against it by the glands C C, 

 which are screwed in round the glass. From each of the socket- 

 pieces B, a tube, D, proceeds with a cock in it and a screw on 

 the end for fixing it into the fire-box ; and the piece E, containing 

 another cock, is screwed into the lower piece, and the plug F into 

 the upper piece, affording the means of putting the glass tube down 

 into its place. When the two cocks in D D are opened, the water 

 of the boiler rises in the glass tube to the same height that it is in 

 the boiler, the upper part of the glass being filled with steam, 

 the height of the water in it shewing always the level of the 

 water in the boiler ; the cocks are for the purpose of stopping 

 the communication, when required, from the gauge being out 

 of order or otherwise. The cock in the piece D is for the purpose of clearing 

 out the gauge, by allowing a stream of water to run through it ; and it is often 

 necessary to open it when examining the gauge, in order to get rid of the bubbles 

 of steam formed by the rapid ebullition of the water, which sometimes render it 

 difficult to ascertain the precise height of the water. The difficulty is also in- 

 creased by the motion of the engine producing oscillation in the water ; but the 

 disturbing effect is much diminished by choking the tube, or making the communica- 

 tion with the boiler through the tube D very small, so as to impede the motion of 

 the water in the tubes. A small plug, G, is screwed in opposite each tube, D, to 

 afford the means of clearing out the tubes D, by passing a wire through them when 

 the plugs G are taken out. 



To afford an additional means of ascertaining the height of the water in the 

 boiler, two gauge cocks, M M, are fixed in the side of the fire-box, one being four 

 inches above the other, and the lower one, one inch above the top of the internal 

 firebox. The boiler is generally filled at starting, until the water runs out at the 

 upper cock ; and during working the water level is kept between the two cocks, 

 and often up to the upper one. The cocks are opened occasionally to try the level, 

 and if steam should ever be found to blow out at the lower cock, showing that there 

 is not more than one inch of water over the roof of the internal fire-box, instant 

 attention has to be paid to the feed-pumps, and the fire damped if necessary, to 



