998 THE COLLIERY GUARDIAN. May 17, 1918. CURRENT SCIENCE AND TECHNOLOGY. Electric Haulage in Mines. Based upon a consideration of the acceleration and retardation of the cage, Mons. F. Robin (Rerue Generale de V Electricite) determines the conditions necessary to reduce the copper losses in the hoist motor to a minimum by an appropriate division of the total time into accelerating, constant speed, and retardation periods. In the simplest cases in which cylindrical winding drums are used, the speed-time diagram is composed of three parts. The first, a period of constant acceleration, the second, a period t2 of constant speed, and a third, a period t3 of constant retardation. The area of this curve represents the depth of the shaft. If the maximum speed V is given, t2 is given by the relation t2 = (2e/V) — T, in which e is the depth of the shaft and T the total time for the hoist; should be chosen so that the acceleration does not exceed the value permissible with the cable used, which may be taken at 1*25 m. /sec.2 for round steel cables, or 1 m./sec.2 for rectangular steel cables. On the other hand, if the speed V is not given, the time T may be divided up in an infinite number of ways. It is shown that for a variety of systems of haulage, the copper losses in the motor are a minimum when t1} t2 and t3 are taken each equal to one-third of the period T. The systems examined included an equipment with a Leonard converter or with a fly- wheel compensating unit, and with haulage gear fitted with cylindrical drums, with or without equilibrating cable, and also with drums of such a nature that the radius on which the cable is wound is constantly varying, and, lastly, with spiraloidal drums. In all of these cases the best arrangement is obtained when the period T is divided into three equal parts. If an installation is already in existence and it is desired to approach this optimum condition, it will generally be found that and t2 are smaller than T/3, and it would be necessary to increase the linear speed of the cage and the angular speed of the motor. This may be done by increasing the voltage of the generator, if this is possible, considering the saturation of the iron, or by weakening the field of the haulage motor, which may not have the desired effect, as the current will be increased thereby. In some cases the optimum division of T is impossible, as the speed of the cage would become too high. This would happen when the shaft is very deep, e.g., 700 to 1,000 m., in which case the speed would exceed the maximum permissible speed of 20 m./sec. In such cases it is sufficient to make tr equal to t.,, t2 being calculated from the maximum permissible speed. A case is worked out of a haulage gear in the mine of Albi, the time of a hoist being 35 secs., and divided in the first instance into three equal periods, and in the second instance into periods tY = t2 = 5 secs., and t2 = 25 secs. The total copper losses are 6’5 per cent, lower in the first case than in the second. Steaming Horizontal Retorts. Mr. R. J. Rew (Gas World) gives details of the experiments carried out at a gasworks making three million cubic feet per annum, and the attempts made to increase the make of gas pel’ ton of coal used by ‘“steaming” incandescent coke in the ordinary fireclay retorts. In ordinary working, the retorts are charged twice daily with 3| cwt. charges. Exhauster is used during the first seven hours of charges and worked at level gauge. Average make of straight coal gas is 11,250 to 11,500 cu. ft. per ton, including 4 to 5 per cent, of air. By simul- taneously steaming one retort, and with 3| cwt. of coal in each of the other two, water used being 2 to 3 gals, per hour per retort, the yield is increased to 14,860 cu. ft. per ton. When the retorts were steamed at night, during the “idle” hours, with no exhauster running, and a back pressure on the retorts of about 40-tenths, each retort produced about half the normal quantity of water gas. Steaming for 14 hours gave a loss of 25 lb. of coke, but about 1,600 cu. ft. of water gas were produced, equal to 15f lb. per thousand cubic feet. Taking the value of coke at 30s. per ton, it means that an extra 1,000 cu. ft. of water gas cost about 2|d., against lOd. per thousand cubic feet for coal gas (after crediting the cost of coal with the coke and tar it would pro- duce) to make an equal additional amount of coal gas. The quality of the coke after seven hours’ steam- ing showed little alteration, but after 14 hours was decidedly smaller, though still saleable. If possible, coke that has been steamed 14 hours should be kept out of the furnace, as the best results were obtained with highest heats. The author states that a steam boiler is an advan- tage, but not a necessity. Surplus coke breeze, if put back into the retorts, can be used equally well for water gas production by steaming. The amount of coke used. in furnace remains normal. Fourteen hours’ steaming is a reasonable limit, if coke has to be afterwards sold. If intermittently charged with coal and steamed, even the worn retorts remain in normal condition. After the first 24 hours’ steam- ing, all carbon scales off the inside of the retorts, which remain perfectly clear. Retorts to be steamed should be charged as full as possible, and preferably with a coal that has a tendency to swell. No adjust- ment has been made to any burner, stove, fire, or engine, since this process was started, nor has any complaint been received. It is necessary for easy working, and to meet everyday conditions, to make a modification to the ordinary fireclay retorts. These special retorts may be steamed at will by simply turn- ing the valve of the steaming appliance. Steam from Natural Springs. The natural steam springs near the ancient city of Volterra, in the Province of Pisa, Tuscany, which are evidently due to latent volcanic activity, are described by Mr. U. Funaioli, in Engineering. These springs have been known for some centuries, but they were only regarded as a natural curiosity, and were the objects of superstitious fear of the surround- ing peasantry till the year 1790, when a chemist of the Tuscan Court, Hoefer by name, and Paolo Mascagni, a professor of the University of Pisa, ascertained the presence of boric acid in the waters contained in one of these springs. The result of this important discovery was the birth of the well-known boracic works currently described in all treatises of chemistry and of geology. The first important plant for the extraction of boric acid from the natural steam springs was inaugurated in 1818 by the firm of Larderel, near the small hamlet of Montecerboli, and the new village which was then built in the immediate neighbourhood of the springs was called, after its founder, Larderello. The steam springs are found in eight localities, distributed in an area of about 100 sq. kiloms., and in each of these localities there are boracic works. In the natural condition, the steam finds its way through crevices in the soil, and sometimes issues at the bottom of small craters filled with water, which is kept at boiling point by the steam, but more often in jets of steam or boiling water direct from the earth. The steam wells now made range from 60 m. to 120 m.; in some instances a depth of 150 m. has been attained before provoking the explosion. The pres- sure of the steam at the point of its delivery depends upon the diameter of the tubes through which it is brought up, and also varies from one locality to another. The highest pressure, in Larderello, measured with closed valves over the soffione, and with no efflux of steam, is about three atmospheres effective. This pressure decreases with the increase of steam output, and the mean pres- sure with maximum output is about 1 atmosphere effective. Accurate observations with recording pressure gauges, continued for several months, have proved that, for a given opening of the stop valves, the pressure of efflux is constant. The output varies in the “ soffioni ’ at Larderello from 3,000 kilogs. of steam per hour, to 14,000 kilogs. The temperature of the steam, measured at the top of the hole during efflux, amounts to 180 degs. Cent., as the steam is superheated by friction against the tubes lining the hole. As to the origin of this steam very little is known. Besides Larderello, other spots situated at distances ranging from a minimum of 3*5 kiloms. to a maximum of about 12 kiloms. from Larderello, present similar phenomena. MINERS AND COAL PRODUCTION. The executive of the Miners’ Federation of Great Britain held a meeting at the Grafton Hotel, London, on Tuesday, to consider the position with reference to coal production. Mr. Robert Smillie, president, was in the chair. Recent developments make it essential that there shall be an increased production of coal from the pits in Great Britain, and particularly at pits producing for the export trade. This comes at a moment when a very large number of the younger and more sturdy workmen under 32 years of age are being taken from the pits for military service, thus putting an additional strain upon the older men. With fewer men available to do the work the needs of the country require a larger output, and an appeal is to be made to the miners to increase their production by more regular work and the fore- going of holidays. There is still a good deal of irregular working by a section of the men which has a serious effect on the general output of coal. A deputation from the Cokemen, an affiliated branch of the Federation, attended, and laid before the e xecu- tive the position as to the last advance in wages granted to them by the award of the Committee on Production. There is dissatisfaction among the men at the allowance for overtime and week-end work at the rate of time and a quarter instead of time and a half, and it is proposed to ask for the levelling up of the overtime rate on the expiration of the period of which the award was made. On Wednesday a national conference of the coal mining industry, convened by the Miners’ Federation of Great Britain, was held at Whitefield’s Tabernacle. The purpose of the conference was to hear an address from Mr. Guy Calthrop, Coal Controller, on the present position of the industry and the need for an increased output to meet the requirements of our own and Allied countries, and to consider a scheme for the setting up of mobility bureaux in the various mining districts to facilitate the transfer of miners from districts where work is slack to districts where a larger output is required. Mr. Smillie was in the chair, and there were present 136 delegates from all the districts in Great Britain. Mr. Guy Calthrop admitted that the industry was working under difficulties caused by the recruitment of a further 100,000 men from the pits; but that was a military necessity, and he appealed to the delegates to impress upon their fellow-workmen the duty, by regu- larity of work and increased effort, to not merely maintain, but to enlarge, the output of coal. It was of the greatest importance to the country that every effort should be made by the workmen at home to support those in the fighting line, and in no industry was it of more vital import than in coal mining. A large number of questions were put to the Con- troller, and it was pointed out that, in taking the men under 32 years of age, the military authorities had taken the strongest and largest producers among the coal hewers, and thus made it more difficult to maintain the average rate of output. Following the Coal Controller’s appeal came a sudden collapse of the conference. The special business for which the delegates had been called together was to consider a scheme for a central mining mobility bureau, drawn up by the executive with the Coal Controller. The main objects of the scheme were (a) To find employment in mines in other districts for miners who are working short time ; (6) To maintain the output of coal in those districts where every ton that can be produced is of importance; and (c) Generally to bring about the more productive utilisation of labour in the coal mining industry. The wages were to be the rate current for the work and the mine at which the man offered to work; with a free railway warrant at the commencement and termination of the employment; together with a subsistence allowance of 17s. 6d. a week if married, or if unmarried the home is mainly dependent upon him, and 10s. 6d. a week if unmarried and the home is partially dependent. The President presented the scheme but not a single delegate rose to move its adoption, and in the absence of any action by the delegates the scheme collapsed. COAL FREIGHTS TO FRENCH PORTS. The Shipping Controller has issued an Order, which amends the limitation of freight rates regarding French ports. A complete table of these rates appeared in the Colliery Guardian of February 15, 1918, and they remain in force for steamers not exceeding 400 tons gross (inclusive of war risk insurance on ship), with the exception of Mersey to Rouen, which is now 36s. 6d. For steamers exceeding 500 tons but not exceeding 750 tons gross (exclusive of cost of war risk insurance on ship) the following new rates are scheduled : Tyne, Hull, and East coast to Marans, 43s. 6d.; ditto to Arcachon or Mortagne, 46s. 9d. ; Mersey to Coueron, 29s. 3d.; ditto to Marans, 31s. 6d.; Arcachon or Mor- tagne, 35s.; Clyde to Coueron, 31s. 3d. ; ditto to Marans, 33s. 6d. ; ditto to Arcachon or Mortagne, 37s. Chantenay and Nantes have been added to the sche- dule. For steamers not exceeding 400 tons gross the rate is 48s. 9d. from Tyne, Hull, and East Coast; 41s. 6d. Bristol Channel; 42s. 9d. Mersey; 45s. Clyde; and 51s. Forth and Fife ports. For steamers exceed- ing 400 but not exceeding 500 tons gross the rate is 39s. Tyne, Hull, and East Coast; 32s. 6d. Bristol Channel; 33s. 6d. Mersey; 36s. 9d. Clyde; and 41s. 3d. Forth and Fife ports. For steamers exceeding 500 but not exceeding 750 tons gross the rate is 35s. 6d. Tyne, Hull, and East Coast; 39s. Bristol Channel; 30s. Mersey; 32s. 3d. Clyde; and 37s. 9d. Forth and Fife ports. For steamers exceeding 750 tons gross the rate is 31s. Tyne, Hull, and East Coast; 25s. Bristol Channel; 26s. Mersey; 28s. Clyde; and 33s. Forth and Fife ports. For steamers exceeding 750 tons gross (exclusive of cost of war risk insurance on ship) the following new rates are in force : Mersey to Arcachon or Mortagne, 31s.; Clyde to Coueron, 28s.; ditto to Marans, 30s.; ditto to Arcachon or Mortagne, 33s. The rate from Amble, Blyth, and Seaham is 3d. per ton, and from Goole 6d. per ton over Tyne, Hull, and East Coast rate. From Llanelly, Neath Abbey, and Burry Port 3d. per ton over Bristol Channel rate. The rates for sailing vessels have been entirely revised, and appear below. They are inclusive of cost of war risk insurance on ship : Sailing vessels fully rigged or dismantled and barges. o O 0) CQ £ '"d tn fl ce g ft -2 § “ fl £ Rouen 83 0 76 0...80 6...85 0...87 3 H avre 78 6...71 6..76 0...80 6...82 9 Dieppe 79 6 . 73 9 . 78 6...82 9...83 9 Dunkirk 85 0...82 9 87 3...92 0...89 9 Calais 82 9...80 6...85 0...89 9...87 3 Boulogne Tr eport, Cherbourg, Fe- 78 6...78 6...82 9...87 3...85 0 camp Caen, Granville, Honfleur, 80 6 ..73 9...78 6. ..83 9...85 0 Trouville ’. 80 3...72 9...77 3...82 9...83 9 St. Brieuc 83 9...75 0...79 6...85 0...88 6 St. Malo, St. Ser van 80 3...68 0...75 0...80 6...85 0 Brest 82 9...68 0...75 0...80 6...87 0 Gravelines 85 0...82 9 . 87 3...90 6...89 9 Duclair, Caudebec St. Valery sur Somme... 1 St. Valery en Caux | 82 9...79 6 . 83 9...88 6...87 3 Courcelles... 1 Port en Bassin i 90 0...85 0...90 0...95 0...95 0 Isigny................ | Carenten .............J Quimper is omitted from the schedule, and quotations for that port should be submitted to the Ministry of Shipping for approval. Patent Fuel and the Price of Pitch.—Patent fuel manu- facturers are concerned about the proposal of the Coal Controller regarding the price of pitch. It was under- stood that when the price of coals was fixed at 30s. for France, pitch would be fixed at 30s. per ton at the w’orks. Recently the Coal Controller has intimated that he had arranged for pitch to be supplied at the works of patent fuel manufacturers at a price of 43s. 6d. per ton. Patent fuel makers object strongly to this pro- posal. Trade Boards Bill.—The Bill introduced by Mr. G. H. Roberts, Minister of Labour, to amend the Trade Boards Act, enables the Minister of Labour to bring a new trade under the Act of 1909 by means of a special Order, instead of by a Provisional Order, which requires a confirming Act of Parliament. It also widens his power to apply the existing Act to new trades, his power in this respect being at present limited to cases where the rate of wages prevailing in any branch of a trade is exceptionally low. By an acceleration of the machinery for the fixing of compulsory minimum rates, it will be possible for a rate to be brought into full operation within three months after it has been proposed by a Trade Board, instead of nine months as required by the existing Act.