May 29, 1914. THE COLLIERY GUARDIAN. 1185 arrangement of crossing sliding members and beams. The sliding members, which are moved to the right or left by means of the lamp lever, are provided with cross arms, which engage above or below the cross beams which are raised or depressed by the switch lever, so that the whole arrangement is independent of the reli- ability of the pointsman. West East Zg North Fig. 8.—Plan of Road Junctions to Pit-eye, showing Tracks, Points and Lamps. Oncoming-train signal 3500- |l ■2000-ft II JI °O°O0 O O O O 0^0 a 9999------- ©OOO©O@OO©O0OC'J signals Fig. 10.—Cross- section. Fig. 9.—Front View of Switch and Signalling Apparatus at the Saturn Colliery. Winding shaft Points worked by compressed an Spring points Fig. 11.—Plan of Pit-eye and Haulage Road Junctions at the Saturn Colliery, showing Tracks, Points and Signals. Signal Nos. DIRECTION OF TRAIN. Signal Levers. Points Levers. Outward. . Inwa rd on ®D ®D (2D HDpD CD CDICD ffiZ i®i Z1 z^ z2 z5 zB 0 5 w F| N z 3 4 5 5 7 Xi IT : From track IH. to east road o o © © o ® i © — — — s „ ,, „ „ south „ 1 © i © — — if w. „ „ „ „ west „ □ □ o © □ e © 9 © — — "T ■ „ ,, ,, _,, Fanny seam © a © o 9 © 9 Il + N ,, >> <> „ north road 9 © © 0 O © 2 From irofthroad to track II. 9 © o e J 3- ,, Fanny seam ,, ,, II. 9 0 o -0 „ west road „ I. © o R i 3 ,, south ,, ,, ,, I. ® • i a © i-m + 5 „ east _,L „ I- © □ |o 7 ,, track I. to winding shaft f £3 ■ o 3 „ „ IT © © J 1 L o i! 1 1 closed. ffl □ Points closed ,, open @ Stop Proceed Fig. 12.—Signalling Plan. The combined apparatus is housed in a niche in the wall of th j main haulage road. Fig. 9 gives a front view of the switch apparatus, and fig. 10 a cross section through same. As in the case of the plant already described, the switches are operated by compressed air, which is admitted through a water trap a and reducing valve b to the pipes leading to the various switch pistons. Visible indicators are provided here also to show when the switch points have been pushed home. The switch lever d is pushed back as far as it will go to close the points, and pulled forward to open them. The lamp lever is horizontal in its middle position, and can be moved up and down, being held in position by a catch engaging in slots. A marble plate in the back of the niche carries the repeating signal lamps and also a series of lamps to warn the signalman when a train is entering the section on any of the roads. This is done by mounting a bare wire, parallel with the trolley wire, in each road, about 70 yards from the signal box, so that as the locomotive trolley pole comes in contact with this wire the corresponding lamp circuit is completed. Another improvement in the apparatus is the provision in front of the empties track III. (fig. 11) of a separate signalling device a, which notifies the driver of the on- coming empty train whether the line is clear, and which haulage road his train will run into. For this purpose each lamp, in addition to a red light, is pro- vided with a plate bearing the initial of the haulage road; and when the line is clear the corresponding plate is illuminated by turning on a light from the signal box. The traffic is regulated by means of the signal plan shown in fig. 12, which is set up in the niche contain- ing the apparatus. The trains coming from the east, south, or wrest road all run on to the No. I. track, whilst those from the north road and Fanny seam run on to No. II. track, being in all cases backed from these tracks up to the shaft. The empties taken out of the cages run down to the collecting tracks, and are replaced by full tubs from Nos. I. and II. tracks. The released locomotives run over the points s6, z5, z3, z1, to No. III. track. A train entering from the east road, for instance, and intended to be run on to No. 1 track, com- pletes the warning lamp circuit and lights No. 6 lamp. The pointsman closes the points z8 and opens £7, z5, and z6; and as soon as the check signals indicate that the points are properly set, moves the signal lever to No. 6, giving “ line clear from east road to track I.” so that the lamp in the east road shows a green light, and the driver can proceed to track I. In the meantime a train of empties from track III. can be run into the northern road, and also a full train from the Fanny seam on to track II., and backed up to the pit eye. In this way three trains can be operated simultaneously, except when a train has to be run from track III. into the western road, in which case only one other train— either from the northern road or from the Fanny seam —can be operated for the time being. A FEW PRACTICAL OBSERVATIONS ON CAS TESTING.* By John Roberts (Wigan) and R. M. Evans. The writers are prompted to contribute these few remarks because they fear there has been a tendency of late to lay too much stress on laboratory experiments and to depreciate the results of the training obtained by practical men in the best of schools—the school of experience. Sir Humphry Davy found that when the safety lamp was placed in 3*3 per cent, of marsh gas, an elongation of the flame resulted. Although all concerned may be ready to admit this phenomenon—though in discussing this subject three or four years ago an inspector of mines stated that we had been “ living in a fool’s paradise ”— some doubt exists as to what extent this indication can be relied upon in testing for gas; and the question has now arisen as to whether a fireman can detect gas when holding the safety lamp on the end of a stick that may be five feet or more in length. Having had experience of the method, both in fiery mines and in the laboratory, and being satisfied as to its reliability, the writers have thought it necessary to defend the system. The misunderstanding on this question is possibly partly accounted for owing to the fact that a certain commercial firm, in describing a particular gas-testing chamber, point out how it can be shown that in this chamber, using a normal flame, a safety lamp may burn in a 5 per cent, mixture without giving any indica- tion of gas; but they omit to state that the lamp may, in certain circumstances, indicate the presence of the gas without reducing the size of the flame. It will be observed that in sections 60 and 67 of the Coal Mines Act, 1911, the percentages named must be found in the general body of the air. This expression has not been defined in the Act, so that one has to use his discretion as to what is meant. The writers would venture to suggest, however, that the general body of the air means the current travelling in such portion of the mine. It is the general practice, nevertheless, to withdraw men and fence off a place if, say, 2| per cent, of gas was found in the upper side of a rib, notwith- standing that the general body of the air shows less than that amount. A careful fireman would not allow a miner to work in a stall where it was found that gas occupied the position shown in the figure. This is as it should be. The general method of testing for gas in such cases is to test the general body of the air first of all. For this purpose the flame is lowered to the standard size for test- ing, that is, Ao in., and the lamp raised very carefully. If there is 1| per cent, or more present, its presence will be revealed in the lamp. In this manner percent- ages ranging between 14 and 5 may be detected and estimated more or less accurately. The caps obtained, with the various percentages, are as follows :—14 per cent., incomplete cap about | in. high; 2 per cent., complete cap about J in. high; 2J per cent., complete cap about f in. high; 3 per cent., com- plete cap about 4 in. high; 34 per cent., complete cap about J in. high; 4 per cent., complete cap about in. high; 44 per cent, complete cap about 24 in, high; 5 per cent., thin cap to top of gauze. Having satisfied himself as to the percentage of gas present, the fireman withdraws his lamp from the impure atmosphere and readjusts the flame to its normal height. In examining his district, it is often necessary for a fireman to examine for gas in cavities several feet above the ordinary level of the roof, and at several points, perhaps, in every road. To do this with the lowered flame requires that he should be able to get up into the cavity. This is seldom convenient, and often more or less impracticable. The fireman not having a ladder on his shoulder must vary the method of testing. He places his lamp on the end of a rod about five or six feet long and raises it slowly and carefully into the cavity, watch- ing for the slightest indication of any elongation of the flame. In this manner, using the normal flame, he can detect the presence of as little as 2 per cent. It is true that the percentage cannot be accurately estimated in this way, as a cap will not be formed, the * Abstracted from the Proceedings of the South Wales Institute of Engineers.