June 1, 1917. THE COLLIERY GUARDIAN. 1033 5. An engine of 200 indicated horse-power is required to ventilate a certain mine. The water gauge is 4 in. The efficiency of the fan and engine combined is 65 per cent. What quantity of air is passing through the mine? (50) 6. Show, by means of a sketch of about three times its natural size, a section through the centre of the flame of a miner’s safety lamp. Include the wick tube and a portion of the wick in the sketch. Describe the various zones in the flame. State which of these zones gives light, and why it does so; which zone is the hottest and which is the coldest; what the coldest zone consists of ; why the flame is lowered when testing for firedamp; why a “cap” appears when’ there is firedamp in the air; and what is the height of the “cap,” measured in fractions of an inch, when 3 per cent, of firedamp is present. (50) 7. Describe how you would measure the quantity of air passing through an airway in a mine :—(a) By means of an anemometer; (b) with dust; (c) with powder smoke in a naked light mine. (50) Subject No. 3.—Explosions in Mines, Underground Fires, and Inundations. (Five questions only to be answered.) 1. A large and important main haulage road, thickly timbered, is heavily coated with coal dust. How would you remove the coal dust prior to using stone dust ? (20) 2. What are the principal objections to the use of water for mitigating the dangers of coal dust? (20) 3. When in charge of recovery work after an explosion, and finding men suffering from the effects of afterdamp, describe the measures of first-aid and care necessary in getting them out of the pit. (20) 4. Enumerate all the most likely causes of fires under- ground, other than gob-fires. (20) 5. When using rescue apparatus, how long may the wearers, be away from the base, how far may they go, how fast should they travel, and how much work can they do as compared with men under ordinary circumstances and not wearing apparatus ? (20) 6. Spontaneous combustion has commenced unexpect- edly in a part of the pit out of reach of direct observa- tion. How would the evidence of heating be first detected, Fig. 4.—Subject No. 5. Surveying, Levelling and Drawing. • (Referred to in Question No. 1 First Class.) and how would its progress be apparent? When would you consider it to be dangerous? (20) Subject No. 4.—Machinery. (Five questions only to be answered.) 1. Give a sketch of a single-riveted lap joint, and also a sketch of a treble-riveted butt joint with inside and out- side cover plates or straps both as used in Lancashire boilers. State which joints of the boiler are generally lap- jointed, and which are generally butt-jointed. (20) 2. In electrical plant what are the differences between a dynamo and a motor? How are motors started? (20) 3. What is an “eccentric” as used on engines? For what purposes are eccentrics used ? Illustrate your answer with one or more sketches. (20) 4. What is the difference between a condensing engine and a non-condensing engine? Why is condensing resorted to ? Describe one form of condenser. (20) 5. State the differences between cast iron, wrought iron, and mild steel, and give examples of some articles or parts of machinery that are best made of each of these materials. (20) 6. Each cage and its empty trams (hutches or tubs) in a shaft weigh 3 tons. The load of coal on the upcoming cage is I ton. At mid-wind the speed is uniform, and is GO ft. per second. What is the horse-power exerted on the moving cages at mid-wind, neglecting friction? (20) 4 Subject No. 5.—Arithmetic and Surveying. (Five questions only to be answered, at least two of them being from the part headed “ Surveying.”) Arithmetic. 1. 'For an output of 2,400 tons the wages paid to coal getters amount to £452 10s., and for other labour <£345. What is cost per ton for each item, and the total cost ? (20) 2. Calculate the weight of water contained in 100 yds. of a column of pipes 12 in. in diameter. What weight of oil of a specific gravity of 0-891 would be contained by a pipe of the same length and diameter? (20) 3. Express 13-37625 acres in acres, roods, poles, or perches, and square yards, and in square yards; and 5 acres 3 roods 39 poles in acres and decimals. (20) 4. If 450 men work 2,484 shifts in six days, (a) what is the percentage of absenteeism? (6) what would be the per- centage loss of output if two-thirds of the time were lost by coal getters, assuming the output to be proportional to the time worked by coal getters who number three-fifths of the men employed ? (20) Surveying. 5. A line measures 1,245 ft. What is the equivalent length in links ? (20) 6. If after completing a short survey you find that your link chain is 3 in. too long, are your measurements longer or shorter than the true length ? If one of the lines measured 1,260 links with the chain, what is its true length ? (20) 7. Describe shortly the operation of levelling with a straight-edge and spirit level. In levelling in a roadway dipping 1 in 2^, or thereabouts, and 44,- ft. in height, what length of straight-edge would you use? (20) 8. Write out the quadrant bearings corresponding to the following circular readings, viz. : 317 degs., 25 degs., 92^degs., 195^degs., and 270 degs. The readings given are the readings of the north end of the needle on a dial reading from left to right, with the north or zero point of the dial leading. (20) Subject No. 6.—Mines Act, General and Special Regula- tions and Orders, and Writing of Reports. (Five questions only to be answered. No. 1 is compulsory.) 1. Compulsory Question.—What is meant by the term “open sparking” as used in the Regulations concerning electricity ? (20) 2. What are the precautionary measures to be carried out when any working is approaching old workings con- taining or likely to contain water? (20). 3. At what different points in a mine is the air to be measured ? (20) 4. Explain clearly the construction of stoppings between the main intake and main return airways to be in accord- ance with the General Regulations under the Act. (20) 5. What are the Regulations to be observed in with- drawing props or other roof supports ? (20) 6. In a self-acting incline, say, 200 yds. long, with a gradient of 1 in 15, what are the various provisions you would have to make to comply with the Coal Mines Act and Regulations ? (20) * . COKE OVEN MANAGERS’ VISIT TO HOLBROOK PLANT. The first of this season’s series of excursion meetings arranged by the Midland Section of the Coke Oven Managers’ Association, was held on Saturday, May 26, when a visit was paid to the Holbrook coke oven and by-product plant of Messrs. J. and G. Wells Limited, at Killamarsh, near Chesterfield. The party, headed by Mr. G. Chrisp (president of the section) numbered about 30, and was conducted round the plant by Messrs. J. Marshall (manager), J. W. Spencer (assistant manager), R. G. Greensmith (chemist), G. Chapman (foreman), and R. Engstrom (electrician). The plant, which has been in operation nine years, con- sists of ten Collin regenerative ovens, and 50 Huessener waste-heat ovens. The coal is first treated at a Dortmund washer, which deals with all the product of the colliery under 4 in., and sorts it into various sizes, all that goes through a % in. mesh being reserved for coking. The capacity of the washer is 75 tons per hour. For the coking slack there are six drainage hoppers, each of which will hold about 90 tons. The system is a very good one, reducing the moisture to a small proportion, sometimes as low as 8 per cent. From the washer the coal is conveyed to the coke oven storage bunker by an aerial rope- way, by Whites of Widnes. This ropeway has been working rather more than six years, and the cost of repairs has been practically nil. The carrying rope is changed about once a year, but the driving rope lasts a long time. From the washery the visitors were taken to the ovens. The output of coke is 6,200 tons per month. The usual by-products are recovered, the yield of benzol being 25,000 gals, per month, equal to 3T gals, per ton of coal carbonised. The output of tar is 3’84 per cent., and that of sulphate of ammonia 1’32 per cent, of the weight of the coal. A good deal of interest was displayed in the con- struction of the oven walls. One of the Collin ovens, which had been going since April 1914 without re- lining, was drawn, and the walls were found to be quite smooth and in first-class order. The waste heat and surplus gas from the ovens is used to heat five boilers for raising steam—four always working and one spare. The steam generates enough electricity to run the whole plant, and give in addition 300 horse-power for use at the colliery. The installation in the power station consists of two 150 kw. Scott and Mountain high-speed engines, coupled direct.to gene- rators, and one 260 kw. Beiliss and Mor com high-speed engine, coupled direct to a Siemens regenerator. At the conclusion of the tour, the visitors were enter- tained to tea by the directors of the company. Mr. Chrisp, who presided, said meetings of that kind were very enjoyable, as they afforded better oppor- tunities for social intercourse than the ordinary meetings of the section. Although that was the first of the series, it was better attended than, some of the other meetings had been. Whilst they had not seen a new plant that day, or anything very modern, they had seen something which was quite a credit to the management and the directors. He was sure it would be of advantage to many young members to follow Mr. Marshall’s example in the set out of the plant, and the way it was worked and kept. They had seen something a little bit out of the usual rut, and many new things had been apparent. The thing that had struck him most was the all-round efficiency of the plant. Of course, that was only what they would expect from a man of Mr. Marshall’s calibre. Mr. Marshall was one of the old members of their association, and one who could have been much more prominent in it than he had been. They very much regretted that he had not been able to take a great share of the work. Mr. T. H. Riley (Tinsley), in proposing a vote of thanks to Mr. Marshall and his directors, said that although the plant was an old one, there was no doubt it was giving good results. He had examined the walls of two of the ovens, and they were in very good con- dition considering the number of years they had been working. He only hoped that the walls at the plant with which he was connected would stand equally well. In the output of by-products, Mr. Marshall was really doing remarkably well. Mr. G. Hebden (Parkgate) seconded. He said that he and the other associate members had been very much interested in what they had seen that afternoon. It was always a pleasure to go round another plant, whether an old one or a new one. They were very grateful for the way they had been ti eated. Mr. Marshall, in reply, said he Lelieved the plant had been very much appreciated by them all, and had also proved somewhat instructive. It was certainly not a new plant, for it had been working nine years, but the test of efficiency was the results that one got. They did get very good results at Holbrook—splendid results, which would take some beating. They got all they possibly could out of the stuff that went into the ovens. The testing of all waste was carried out on the most scientific lines. They did not allow anything to go down the drains that they could prevent, hence the good results. If the same were care taken at other plants, probably some other people would be doing just as well as they were doing at Holbrook, if not better. Probably the plant had looked extraordinary to some of them who had had dealings with modern plants of the semi- direct and direct process type. He referred to the number of towers, scrubbers and coolers that they had about Holbrook, but that was nothing to go by. As he had said, it was the results of the working which showed the efficiency of the plant. The next meeting of the section will be held on June 30, when the Rockingham plant will be visited. AERIAL ROPEWAYS FOR FOREST WORK. In a paper read before the South Wales Institute of Engineers on May 25, Mr. J. W. White supple- mented his paper on aerial wire ropeways (Colliery Guardian, March 30, 1917, p. 621) with observations on the use of ropeways for transporting timber from forests to the railway or the highway. He said there were two ways in which these ropeways could be employed: (a) In the forests themselves as feeder lines; (b) from the forest to the railway or highway. As feeder lines in the forests, they could be used either to bring the trees to one central point for despatch to the railway, or, if a sawmill was used in the forest, to bring the tree trunks up to the mill. They were readily taken down and re-erected as often as required without damage, so as to follow up the trees as felling proceeded; and a series of such feeder lines could be quickly erected, radiating in all directions from the sawmill or main despatching point, to bring the felled trees up to the sawmill. Such lines were particularly useful if the forest was traversed—as was often the case—by streams and small valleys, as they would save all the cost of levelling the land surface and the pre- paration of a relatively even formation, which would be necessary for a tramway or a cart road. The separate ropes of each span were easy to handle and tighten up, even of sufficient length, if needed, to carry heavy individual loads up to five tons each. If short spans were used, the sag of the rope in the middle of a span was not excessive, being only 2 or 3 ft. with a 90 ft. span, thus making animal traction simple and efficient. Portable ropeways built on the author’s sectional system, as already described, appeared to lend themselves particularly to this work, especially where animal traction could be introduced, owing to the great elasticity possible by this arrange- ment. In this system a separate carrying rope was used for each span of the line, on which the loaded carriers travelled, as in the ordinary bi-cable system Brackets with special rope saddles could be. readily attached to the trunks of trees, to be left standing, more or less in line, for the purpose, as the felling of the timber proceeded. It was not necessary for the trees to be even approximately in line, as deviations from the straight line, either vertically or horizon- tally, could be made at every tree standard if required, and if there were no single trees reasonably in line, span ropes could be stretched from any pair of trees, and the rope-supporting saddles suspended from the span ropes, so as to maintain a reasonably even line. A smooth track for the carrier wheels was provided from one rope to the next, and in order to save the complication of mechanical traction, animal traction was used. The horses (or other animals) drew the loaded carriers along the ropeway by means of ordi- nary. tow-ropes in much the same manner as barges were towed by horses along canals. The next problem was to transport the more or less sawn and prepared timber down to the railway or high- way. And here nature came to their help. The bulk of the forests and plantations in this country were on the tops or sides of mountains, so that the loads gener- ally had to travel downhill, the gradient in most cases being sufficient for the descending loads to draw up the empty carriers without the necessity of employing power. In such cases, two main carrying ropes were employed, on which the carriers travelled up and down either by two separate main-and-tail ropes, or, if the gradient should be undulating, by an endless haulage rope. In either case, the haulage rope was coiled around a brake drum at the top of the incline, and provided with sufficient brake power to enable the speed of the descending load to be rapidly controlled on its passage downwards. If there should be any distance of relatively flat land to be traversed from the foot of the mountain to the railway, it was a question of local conditions as to whether it would be prefer- able to continue the ropeway from the foot of the hill- side to the railway, and convey the loads along it by mechanical or horse haulage, or to lay down a narrow- gauge surface tramway through the fields or along the roadside, and draw the loads by means of a light loco- motive. Bearing in mind the probable temporary nature of the installation, where high efficiency in working costs was not so important as low initial expenditure, the latter method was probably the better in most cases, where the nature of the country lent itself to the quick construction of a tramway. But if the surface of the land was undulating and uneven, with streams or roads, etc., to cross, then perhaps the ropeway was again the more efficient, even if mechanical traction should be necessary.