May 8, 1914. THE COLLIERY GUARDIAN. 1009 when it comes to the recess it jumps forward and so on; the time taken to pass over each raised part may be varied in either direction by the needle valves K K, while the cataract cylinder is kept solid by suction valves L L. The cataract cylinder is submerged in the fluid which is entirely enclosed in order that it may keep, clean and require renewing infrequently. During such periods the pump can be automatic- ally loaded and unloaded by opening and closing valves, which connect the accumulator pilot valve with the by-pass valve and disconnect the gear, in which case the pump is started up unloaded by hand by withdrawing the catch pm in the con- troller handle, which engages with the top of the gear wheel. It will be noted that the by-pass valve F is made acorn-shaped so that it shall open and close gradually; a non-return valve must be placed between the by-pass valve and accumulator. In gears used for air compressors suitable motive cylinder and valves are substituted. THE “SCHOELLER” PATENT CAS INDICATOR FOR MINERS’ LAMPS. With the increased vogue of the electric miners’ lamp in coal mines, unsparing efforts have been made during the last year or two to devise a method of detecting inflammable gas that can be suitably incorporated with the lamp. This, it has been felt—if we leave out of consideration defects that have mainly arisen from the accumulator—would place the electric lamp upon a basis of equality with the oil safety lamp, to which for certain pur- poses it is admittedly superior. Various methods have been devised to achieve this end, the majority based upon the absorptive property of plantinum black or the registration of heat upon materials of high conductivity. Not one of these devices, however, has established a footing of practical utility in association with the electric safety lamp, some failing to give a sufficiently low indication of fire damp, whilst nearly all of them, in use under actual working conditions, have proved unreliable and subject to deterioration. We have been given the opportunity lately of inspecting a lamp embodying a device which is not only simple and applicable in the highest sense, but has survived the ordeal of exhaustive tests in the “ Schoeller ” Electric Miner's Lamp FITTED WITH GAS INDICATOR. mine and laboratory. The principle upon which the Schoeller detector, the device in question, pro- ceeds is not new, the principle of the diffusion of gases having attracted many inventors in the past, of whom the best known in this country, perhaps, are Ansell and Prested. The well known principle of gaseous diffusion is based upon Graham’s law, viz. : “The rates of diffusion of gases vary inversely as the square roots of their densities.” In practice, however, it has proved a matter of considerable difficulty to apply the principle to the miner’s lamp. In the Schoeller indicator a diffusing chamber is attached to the head of the miner’s lamp, the base of sucii chamber being, in fact, formed by the roof of the lamp, the chamber being closed by a ceramic diffusion plate, which is made airtight by suitable washers. Attached to this diffusion chamber is a U-shaped glass tube so disposed that it is in line with the filament of the electric lamp. One limb of this U-shaped glass tube is connected with the outer atmosphere, i.e., the interior of the lamp— the second limb opens to the inside of the diffu- sion chamber. The U-shaped glass tube is partly filled with a suitably coloured signalling fluid, and is suitably calibrated or fitted with coloured glass projections, to indicate the percen- tage of gas met with. The action of the indicator is as follows: When the lamp is introduced into an atmosphere con- taining a gas which is lighter than air (such as firedamp), such gas is diffused through the diffu- sion plate previously referred to; to employ popular language, the gas enters the diffusion chamber more rapidly than the air can escape, and the resulting excess pressure is reflected on the fluid in the limb of the U-shaped tube which is connected to the diffusion chamber, with the result that the liquid rises in the left hand tube, the rise being strictly in proportion to the quantity of gas contained in the atmosphere surrounding the lamp. The “U”-shaped tube is so arranged that the rise of the dark liquid in one or other of the two limbs of the tube is cast across the filament of the lamp, with the result that the light is partially obscured, thus supplying an automatic signal to the miner althougn the lamp may be placed at his back. In the case of asphyxiating gases such as CO2, i.e., those which are heavier than air, the liquid rises in the opposite limb to that which indicates gases lighter than air, i.e., the process of diffusion is reversed. A well known feature of diffusive action is its permanence; in other words, gases that have be- come diffused will never again separate into a heavier and a lighter layer. This is provided for in this case by fitting the diffusion chamber with a valve by which the surrounding atmosphere can be freely admitted; instantly this valve is opened the pressure in the diffusion chamber is brought back to the normal level of the surrounding atmosphere. Thus the lamp is ready for a further test. The primary objection has been taken to an appliance of this nature in that the pressure has a tendency to equilibrate itself in the U-shaped tube, after the lamp has remained for some time in an explosive mixture. This only means that strictly the indicator is not continuously auto- matic, in the same sense that an oil safety lamp does not automatically register the presence of fire- damp. In the latter case the lamp wick must be adjusted to the proper level; in the case of the Schoeller indicator, if there is any suspicion of saturation it is only necessary to breathe gently on the lamp, which by diffusing pure air into the chamber gives a temporary indication in the oppo- site direction, and thus enables a positive and reliable record to be instantly obtained. One of the main defects of diffusion apparatus in the past has arisen from the liability of the porous substance to become clogged with dust, thus lower- ing its permeability. We understand, however, that, owing to its arrangement, the Schoeller indi- cator has in practice proved immune from this defect. The addition of a thin sheet of tissue paper to the diaphragm is an effective precaution. On the other hand, the device is strikingly simple, is extremely adaptable, being so located with refer- ence to the lamp proper as to necessitate no incon- venient variation in design or addition to weight or size, whilst the indicator itself is amply pro- tected from external injury. The indicator is so sensitive as to show the slight quantities of carbonic acid gas exhaled by the human breath, an indication exceeding | in. being supplied in the case of a healthy human being; in the case of firedamp a distinct indication is sup- plied with a mixture containing only 0.3 per cent, of CH4. The cost of attaching the indicator to an electric miner’s lamp (it can, of course, be fitted to any other lamp) is less than Is. We may add that the device is one of those com- peting for the prize offered two years ago by the Dortmund Mine Owners’ Association. The award of the committee has not yet been made, but we understand that this is one of. the few indicators that have survived the eliminating trials. Already several of the largest makers of electric miners’ lamps have taken out licences for its use. In this country the agency is held by Mr. W. Schmahl, of 6, Farringdon-avenue, E.O. The Schoeller lamp, in which we saw the indicator embodied, itself possesses many good features. The accumulator, which is rectangular, is contained in a light cylindrical vessel, which may be removed from the corrugated battery chamber for purposes such as recharging; it is prevented from rotating in the latter by means of a dowel pin cast in the base of the vessel. The bulb is sup- ported on a spring, placed at the base instead of the top—as in the case of the “Ceag” lamp—any breakage of the bulb, therefore, immediately break- ing the circuit. The lantern is very strongly and compactly constructed. The lamp as a whole is rather on the heavy side, but the intention, on the other hand, is to use a pressure of 6 volts. Con- tact is made by a quarter turn of the lantern; the lamp is locked magnetically. APPROVED SAFETY LAMPS. (Continued from page 969.) Flame Safety Lamps Approved for General Use— (continued) The Wolf Safety Lamp No. 7. The Wolf Safety Lamp No. 7, the general design of which is shown in fig. 17, is a double gauze, flame, oil or spirit lamp, with air-feed through vertical and horizontal holes in the middle ring, and through an air-admission ring protected by double gauzes situated below the glass. It consists of the following essential parts :— (1.) Sonnet or Shield of stamped or riveted steel, with an additional securely fastened steel or brass crown. Furnished with outlet holes immediately below the crown, provided that the bottoms of the holes are not below the top of the outer gauze. (2.) Middle Ring, of brass, riveted to bonnet, provided with vertical air-inlet holes of total area not exceeding 0'3 square inch, and with additional horizontal slots of total area not exceeding 0'75 square inch, protected by a baffle ring formed by the inner flange of the middle ring as shown in fig. 17. Pillars, of brass, four, or more, so arranged that a straight line touching the exterior parts of adjacent pillars does not touch the glass. Provided that lamps now in use fitted with four pillars and not fulfilling the foregoing requirement may continue to be used until January 1, 1916. Fig. 17.—Wolf Lamp No. 7. (Cremer Lamp and Engineering Company Limited.) Bottom Ring, of brass, of the type shown in fig. 17, with a flanged ring forming a baffle against a horizontal current entering the air admission slots. (3.) Gauzes of not less than 28 S.W.G. steel wire, 784 meshes to the square inch, with double folded lap seams, formed to fit flanges of the inner and outer base rings, and so secured to the same by punch indentations or rivets as to make strong and flametight joints. The arrangement of the gauzes in the lamp is that shown in fig. 17, and is such that the deep copper flange of the outer gauze ring clearly indicates its presence in the lamp. Internal dimensions. Outer gauze. Inner gauze. Height from shoulder of hoop.............. 4 in. ± 1 in. ... 3} in. ± J in. (or 3 in. ± I in.) (or 2| in. ± J in.) Diameter at top..... 1H in. ± J in. ... 11 in. ± 1 in. (or If in. ± t in ) Diameter at bottom 2-V in. ± J in. ... 1J in. ± J in. (4.) Glass, of an approved type, cylindrical in form, and within the dimension limits and bearing the size mark specified below. Furnished with top and bottom asbestos washers to ensure flametight joints with the gauzes and retaining ring. External diameter........... 59 mm. Height...................... 60 mm. Size mark................... 59-60 (+0 mm. 1 -1 mm. ± 1 mm. (5.) Glass Retaining and Air Admission Ring.—A combined glass retaining and air admission ring of the type shown in fig. 17. with 6 slots, protected by double securely fastened brass gauzes of not less than 28 S.W.G., 784 meshes to the square inch, the total area of the slots being not greater than 0'75 square inch. (6) Oil or Spirit Vessel of stamped steel, with a securely fastened brass screwed ring to fit the bottom ring, with slots cut in the threads to engage the pawl of the magnetic lock. Of capacity sufficient to provide the required light for the required time as specified. Fitted with a flat /-j to % inch burner; and with or without a thumb-screw wick adjuster and an electric igniter of the type shown in fig. 17, both so fitted as not to cause the lamp to be dangerous in an explosive atmosphere. (7.) Locking Device.—One or other of the following:— (i.) A magnetic lock of the type shown in fig. 17, so constructed that the pawl which engages with slots in the oil vessel can be withdrawn only by a powerful magnet. (ii.) A lead-rivet lock with a lug cast on the bottom ring, and a second lug securely soldered to the oil vessel.