January 22, 1915. 188 ________________ 1. Nature of the top immediately above the coal seam, its comparative strength and liability to disintegration upon exposure to the atmosphere. To compensate for this condition, the allowance to be made can be determined by observing the nature of the top in places that have been mined nearest to the location under consideration. Every vein and section may present different conditions, so that allowances varying from 1 to 10 ft. may be found necessary. 2. Nature and thickness of the vein, the ability of the pillars to resist squeezing, and the liability of disturbance to the overlying strata, due to caving or squeezing in underlying veins. To compensate for these conditions is more difficult, for the reason that a squeeze will crack the overlying strata and admit water in varying quantities, although the thickness of rock cover may be far in excess of any requirement against caving. Consequently, there would be no necessity for making any allowances in the rock cover thickness for these conditions. It would, however, be advisable to compen- sate against squeezing in the vein, over which the rock cover is being established, by mining with a larger factor of safety. 3. Probable errors in relative vertical location of top of rock and mine workings. To compensate for possible errors in vertical locations an allowance of 5 ft. in the thickness of the rock should be made. The compensa- tion for this condition will depend upon the verification of surveys on the surface with those in the mine, and unless the elevations are absolutely verified an allowance of at least 5 ft. in the rock cover should be made. 4. Possibility of the existence of deep gorges and pot holes. To compensate for possible gorges and pot holes an allowance of 35 ft. should be made. The thickness of rock cover required for 24 ft. width of chambers to support safely the overlying strata at various depths is graphically illustrated in fig. 3. The curve A is derived from the equation d — 1*5 V d’ and represents the minimum thicknesses of rock where all conditions are absolutely known. This curve could rarely, if ever, be considered in practice, for the reasons before given. THE COLLIERY GUARDIAN. PITHEAD BATHS AT A FRENCH COLLIERY. Last year the Societe de 1’Industrie Minerale paid a visit to the Carvin Mines, where the members had the opportunity of inspecting the installation of pithead baths which was put into service towards the end of 1913. The Cavvin Company are one of the few French collieries that have adopted a system of copartnery, this having been in operation since 1898, and have always displayed a wholesome solicitude for the welfare of their workmen. The baths occupy a site of 45 by 30 metres, a small portion, 15 by 15 metres, being reserved for water-closets, of which there are 22 on the septic tank principle; two of these are for the use of females. The baths establishment is divided into eight bays of 30 by 4’20 metres, and three bays of 15 by 4 20 metres, the larger bays being reserved for the underground workers, and the smaller bays for the workers on the surface; they comprise 60 and 30 separate cabins respectively, giving a total of 570. Water is obtained, at a tempera- ture of about 35 degs., from two water towers of 40 cubic metres capacity. The framework of the building is constructed of armoured concrete on the Hennebique principle, and comprises 75 columns 20 cm. square, bound to a height of 3*50 metres by ties 25 by 15 cm., and at a height of 7 metres by beams measuring 29 by 15 cm., which support the fiat roof. The walls are bricked in to a thickness of 34 cm. The roof is also constructed of armoured concrete, and is covered with a bed of gravel 12 cm. thick, skylights fitted with movable blinds being let in above the bays. The facade is ornamentally constructed in bricks of different colours, and is flanked by two towers which afford access to the roof and act also to assist the ventilation of the building. A balustrade surrounds the roof, and a clock is placed in the centre of the facade. Each cabin occupies a useful space of 1 by 1’60 metres. The partitions are 1'80 m. in height, of armoured con- ... _________________________________ 30 cm. square. Each is surrounded by a frame of wood, with a cork integument, to prevent the loss of heat. They are covered with the same material. Below the reservoir are situated the heating installation, lighting switches, storerooms, &c. Each workman has a certain number, corresponding to a cabin allotted to him. As soon as he has ascended the shaft and handed in his lamp, he seeks his cabin and stays there as long as he pleases—in practice from 15 to 20 minutes. As a rule two workmen are grouped to each cabin, almost always members of the same family, one using the bath at the beginning of the ascent and the other at the end, or the men may be on different shifts. Practically 36 litres of water suffices for a bath. The scheme was introduced gradually, on the completion of each set of 30 cabins, and at the outset each workman, before using the baths, was given a printed notice briefly describing the facilities provided. To this the company added the following injunction:— We hope that this installation of baths, conceived with the view of contributing to the greater wellbeing of each workman, will be appreciated by him, and that he will regard it as a matter of honour to conduct himself with propriety and to observe discipline, so as to render the use of the baths convenient and agreeable to all. Nearly all the underground workmen have availed themselves of the baths—95 per cent, to be exact—and the remainder have special reasons for preferring the seclusion of their own homes. The greatest liberty of action has been allowed throughout on this point. The baths are less popular with the surfacemen, only about 50 per cent, of whom use the installation. The cost of the installation has been as follows :— Fr. Building __........................... 62.277'47 Cabins (including tiles, &cj _________ 39,491'73 Pipes, ironwork, &c___________________ 25,886'00 Heating pipes..................................... 1,683‘05 Chests and hangers................. 4,047’00 Enamelled plaques ................. 237’00 Electric lighting ................... 863’35 ' Bn r diO u 'rip] , ib Big r 'n t—-1 - h UVp -a a fW _o Pigs. 1-3.—Plan, Front Elevation, and Cross Section of Bath-house at the Qarvin Colliery, Total ____________________________ 134,486’60 Water towers_________________________ 12,970’18 Fig. 2.—Section through Cabins. AS Curve B represents the minimum values for the thick- ness of rock cover d after making an allowance of 5 ft. for probable errors in relative elevations, and would only be used when the top rock of the vein is hard, strong sandstone or other rock of equivalent strength and durability. This curve could only be considered when the contour of the top of rock is absolutely known and there is no possibility of the existence of pots or deep eroded gorges. Curve C represents the minimum values for the thickness of rock cover after making an allowance of 10 ft. for poor top in addition to the 5 ft. for probable errors. This curve could only be con- sidered when other conditions as required for curve B are known. Curves D and E represent the values for the thickness of rock cover after making an allowance in each case of 35 ft. for pots and gorges in addition to the allowances made for curves B and C respectively. Curve D would be used when the top is hard sandstone, and curve E when the top is soft and disintegrating. Conditions may warrant the reduction of the allowances as used in determining curves D and E, but unless these conditions are positively proved, it would not seem advisable to mine with less rock cover than is represented by curve D. The practices in mining under wash of various depths have not been very consistent, and it is with the idea of standardising future practice and at the same time securing more safety and efficiency in mining under these conditions that this paper is presented. __________________________ Sir James Bell has been appointed chairman of the Glasgow and South-Western Bail way Company in room of Mr. Caird, resigned. crete and 7 cm. thick. The door gives an opening of 50 cm., with handle outside and bolt inside. In the corner of each cabin is a chest secured by a padlock ; in this the workman can keep his washing utensils, &c., and it acts also as a seat. The floor is of concrete, into which pierced flags are let, and water is carried away in drains which run the whole length of the building and are protected by gratings. The shower batb is normally placed against the wall; on being brought above the flag it is automatically operated, but the workman is obliged to shut it off before he can clothe himself. The water is delivered from the water tower in a main, 1’60 mm. diameter, running across the building. From this main, branches, 50 mm. diameter, extend right and left along each line of cabins, and each line can be isolated from the general circuit. The building can be flushed from the same source of supply. The supply pipes are all constructed of cast iron, while the shower bath pipes are made of steel. The building is heated by steam obtained direct from boilers, and passing through a pressure-reducing apparatus, and the system is so arranged as to accelerate the drying of the clothes. Lighting is obtained from 23 incandescent lamps of 400-candle power, the cabins being illuminated on the basis of 8-candle power per square metre. The method of suspending the workmen’s clothes is novel. Each cabin is provided with a pole, furnished with four double hooks, which can be hung on a rail running across the cabin at a height of 3'30 m. There are two water-towers, but one only is utilised, the other being held in reserve against a possible shortage of water, &c. They are constructed of armoured concrete, and each supported by four pillars This gives a price of 9 fr. per square metre, or 235 fr. per cabin for two workmen. The cost of upkeep may be stated as follows :— Fr. per day. Cleaning ............................. 6’0..... Upkeep of taps, Ac.................... 0’50 Annual painting ..................... 5’00 Coal for heating ...................____ 34’00 Total............................ 45’50 Allotting 5 per cent, interest on the first cost of say 150,000 fr., the daily cost works out at 4’43 c. per bath, or taking the number of baths actually used, about 850 per day, at 5’94 c. The system of separate cabins which has been adopted at Carvin obviously necessitates a larger site area, but it enables the workman to wash himself cltez l/ui; the workmen being sure of finding their cabins unoccupied, do not crowd into the cages, nor have they to incommode themselves by hastening to make room for others. The workmen at Carvin apparently are favourably disposed towards the baths, and the costs are not inordinately high. In 1910, M. Libert gave the following figures as representing the cost of similar installations in Belgium :— No. of Colliery. No. of No. of Cost per workmen cabins. hangers. bath. Centimes. using the baths. Abhooz 30 . .. 560 .. 3-5 450 Monceau - Fontaine No. 14 71 . .. 500 .. 4’4 375 Esperance Bonne- Fortune 42 . .. 630 .. . 4 to 5 ... 400-560 Monceau -Fontaine No. 17 56 . .. 428 .. 6’2 280 St. Nicholas 44 . .. 608 . 6’6 ... 450-579