302 THE COLLIERY GUARDIAN. August 18, 1916. overload trips, two trifurcating boxes, and a mechanical attachment by means of which the circuit may be opened in case the brakes should be applied undeir any emergency condition. In addition, there is an auxiliary panel of similar design, to control the high tension side of the step-down transformer. The connections to the transformer are taken from the machine side of the main switch, the bus-bar chamber being fitted with inter- connecting bus bars for this purpose. To control the low tension circuits to the solenoid, pump motor, and compressor motor, there are provided two sets of three- pole enclosed switches and fuses. The auxiliary apparatus, also supplied by the British Westinghouse Company, comprises :— A 10 k.v.a. three-phase 50 per 3,000/440 volt oil insu- lated self-cooled transformer, to supply the solenoid, pump motor, and the compressor motors; a no-volt solenoid arranged to operate the emergency trip gear for the brakes in case of failure of voltage or (through the action of the overload trips on the main circuit breaker) of overload; a set of drivers’ instruments (ammeter and voltmeter), of the illuminated dial type, with large open scales, and mounted on a suitable bracket on the depth indicator so that the driver can watch the instruments and the depth indicator simultaneously; and a squirrel- DEPTH » 350 YDS B H. P ~ Tint. Diagram Net Load *3400 Its Cace LChain - 2. tons. 300 too too 200 IO 360 HP Drum Speed 42 R ph 20 up 117 HP 60 80 SO Rope. ■ i'bia Runnine, Time • 60 sec Veckinc Time - 50 sec Riol OH - 220 bhp 360 urn Supply-3 50a/3000 v 20 30 i-o Tinc - Secs Time Diagram of Winding from 350 yds. EXPLOSIVE GAS IN COAL MINES. Its Source and Origin. By Norton Tompkins. The opinions expressed in this article are based on the main principles and evidences brought to light in collect- ing the material for a treatise on Bath thermal springs; and whilst at first sight it may appear incongruous to mix up Bath thermal springs with coal mine gas, the connection between the two will appear when it is shown that the heat of Bath waters, and the heat which generates coal mine gas, both proceed from the same source, established on facts drawn from that part of Somersetshire traversed by the waters of Bath springs. In introducing the subject, it will first be necessary to describe that line of volcanic disturbance or mountain chain termed “ The Backbone of England." There can be no doubt that it was the first initiation of our island, so far back as the close of the Silurian and commence- ment of the old red sandstone periods — a period of great and. general convulsions of the crust of the earth, originating all the Leading mountain chains, at any rate of Europe. But what concerns our subject dates from the second volcanic period, that which took place at the close of the great palaeozoic and the commencement of the secondary systems of the earth’s history, when the volcanic energy invariably followed the same lines. Those lines, as a rule, in the United Kingdom, took a north- ally result in fracturing the affected area, producing four vertical faults dividing the carboniferous basin into four approximately equal parts, radiating from the centre of the basin and the centre of the volcanic abyss which originated the basin, and extending through the carboni- ferous limestone which formed the margin of the basin. First, there is the Clandown fault, which runs south, cutting through the north and south anticlinals of the Mendip range at Downhead Mendip. Secondly, the extension of that fault from Clandown to Dunkerton, and its probable continuation to Bath, intersecting the lime- stone between that city and Batheaston. A third arterial fault starts from Dunkerton to Farnsborough, and, in all probability, takes a straight course to the Avon gorge at Hotwells, Bristol; whilst a fourth starts from near Clandown, passes Glutton Union, and, we have reason to believe, may wheel round a little to the south-east, and head for the gorge at Cheddar. Those four arterial faults have been proved in the colliery workings at Radstock,, Huish, and Kilmersdon pits; Clandown,Paulton,and Glutton, in the upper and second series; and in the lower series at Newbury and Mackin- tosh. It must naturally be concluded that they extend down through the whole of the carboniferous system to the plutonic base which brought them into being, and also that the conversion of the horizontal plane into the concave would open out the lower part of the faults, into which the molten plutonic material would be forced, forming intrusive plutonic rocks. When the heated material comes in contact with beds of coal so inter- sected, coal gas is generated, which permeates strata loosened, disturbed, or fractured, unless such permea- tion is checked by infillings of impervious material. By this means the Radsbock and Farrington Gurney series have been saved from explosive gas, whilst, otherwise, the great arterial faults would no doubt be the means of conveying gas to the upper series, from the third series, 2,000 ft. below, which undoubtedly has come in contact with the heat of the plutonic rock. It has been stated above that the surface of the Rad- stock coal basin is divided into four parts by the four great faults; and that the four great faults descend to the molten abyss which gave them birth. That divi- sion of the coal basin which comes between the Clan- down fault and Glutton Union fault is downcast 100 to 120 fms. below the other three divisions. It may be assumed from this that the northern angle of that divi- sion was situated more centrally over the volcanic abyss where the molten material was considerably more fluid than under the other three divisions. Thus sinking, it forced the fluid material through its easiest vent to the surface, viz., the fractured limestone on the same side of the Clandown fault as the sinking strata in the axis of the Mendip range at Downhead. Here it burst through to the surface in enormous volume, now known cage motor of 5 B.h.p. capacity for driving the air com- pressor. A Westinghouse overspeed device is provided, which can be arranged in conjunction with the other emer- gency gear to operate the brakes and cut off the supply of power to the motor in the event of a pre-determined speed being exceeded during any part of the wind, either during acceleration, full speed run, or retardation. This device consists of a small direct-current series-wound generator, driven from the shaft of the winding drum or motor, and arranged to operate in conjunction with a rheostat, which latter is controlled by the depth indi- cator in such a way that a certain voltage is never exceeded, provided the speed is kept within a pre-deter- mined limit. In the event of the pre-determined speed being exceeded during any part of the wind, the voltage of this small machine rises, and so operates a relay in conjunction with the circuit breaker and the emergency brakes. The mechanical parts for the winding engine have been supplied by Messrs. Robey and Company, of Lincoln. The current for the winding engine is generated at the Rockingham Colliery, which is about two miles away, by means of an exhaust steam turbine of the Curtis type, supplied by the British Thomson-Houston Com- pany, of Rugby. The turbine is coupled direct to a 600'k.v.a. alternator. This unit is also capable of being synchronised with a 500 k.v.a. Bruce Peebles alternating current generator, coupled to a 500 horse-power four- cylinder National gas engine set, to form one large unit. The steel headgear in connection with the shaft has been manufactured by Messrs. Newton, Chambers and Company, at their Thorncliffe Iron Works. Mr. Runciman on the Coal Problem.—In his speech at the Chamber of Commerce, Milan, on August 12, Mr. Runciman said that he knew how legitimate was the demand of Italy on the subject of coal, and he pointed out to his hearers the difficulties which Great Britain had to overcome in view of the increased demand and the falling off of production. Nevertheless, Great Britain had shown from the first her anxiety to meet the needs of Italy, and it was probable, as a result of the conversations he had had with Signori Denava and Arlotta, that in the near future the supply of necessaries to Italy would be assured. With regard to the high price of coal in Italy, that was due to the necessity of having recourse to neutral shipping to transport it. The question was, how- ever, thoroughly discussed in the recent conversations, and he believed that the result of those conversations would be to bring about a reduction of the price of coal in Italy. The co-operation and the goodwill of the British ship owners and colliery interests would not be wanting, and would result in such a success as had been achieved in the case of France. The French Government was co-operating with them in this matter of the union of the commercial interests of the Allies and M. Clernentel (the French Minister of Commerce) had authorised him to state that the French Government was very willing to facilitate the transit of Italian products through France to England, notably by con- cessions in regard to the speed of freight trains. ' - ............................................... General View of Pithead Gear. west and south-east direction, and it may therefore be assumed that the volcanic energy of this country formed part of the line which extended from the Pyrenees to the Channel Islands, Cornwall, Wales, the Highlands of Scotland, and Hecla in Ireland. And it is safe to assume that the electrical current of that line is not extinct at the present day, the frequency of volcanic tremors and shocks demonstrating its activity. How- ever, as long as Hecla continues to be the vent and safety valve of that electrical current, so long shall we be free from anything more serious, and will it continue to be the warming pan for the waters of Bath springs.' It is admitted that all carboniferous strata were laid down in horizontal beds. At the second period of extra- ordinary volcanic energy, already mentioned, certain zones on the east flank of that volcanic line, deep in the earth’s crust, and probably beneath all aqueous strata, became the focus of electrical energy, fusing the earlier pateozoic strata into a liquid lake. The result of this was to convert that horizontal plane of the more recent paleeozoic, or carboniferous, system into a concave, or, what is now termed the coal measure basin, by plunging into its liquid foundation. The liquid, under the pres- sure of 60 or 70 square miles of strata, 8,000 or 10,000 ft. thick, escaped at the point of least resistance, viz., the line of fracture between the electrical zone and the unaffected surrounding strata, the margin of the basin, the Mendip range from Bristol to Frome, and its con- tinuation to Hinton Charterhouse, Bath, Chipping Sod- bury, and surrounding the Gloucestershire coal field. The conversion of the plane into the concave would natur- ae the igneous dyke, extending from Downhead to Moon’s Hill, and to Stoke Lane, between the north and south anticlinals of Mendip—at present three miles long and about a furlong wide. When the eruptive force was at its greatest, there is no evidence that its length was greater, but conclusive evidence exists that its width from north to south could not have been less than a mile. Thus an eruptive neck of not less than three square miles was forced open to allow the exit of liquid material under the pressure of 8,000 or 10,000 ft. of sink- ing strata, over an area of 12 square miles. The erup- tive force could not extend to the.south, the undisturbed ground being unyielding. To the north the strata lent itself to the uplifting force titlting it up, and throwing it over, reversing its dip from a north dip to a south dip of 45degs., as is so much in evidence at Newbury and Mackintosh Colliery. This action, in widening the opening of the dyke, moved northwards the strata, over an area of three miles south to north, and three miles east to west. The strata moved was, vertically, in the shape of a wedge, and at the dyke its thickness must be 3,000 to 4,000ft., thinning out at Foxcote, Lower Writhlington, north of Radstock, and near New Rock Collieries. This movement is known to miners as the slide, or overlap fault, and has been the occasion of a great number of minor faults of a crumpling descrip- tion resembling the waves of the sea, but has no connec- tion whatever with coal gas. This account of the igneous dyke and the chief faults of the Radstock coal field is given to show the magni- tude and character of the great gas generator and its