966 THE COLLIERY GUARDIAN. May. 7, 1915. CURRENT SCIENCE AND TECHNOLOGY. Formulas for Miners’ Lamp Glasses. Recent work done by the Glass Research Committee appointed by the Institute of Chemistry has included the investigation of suitable formulas for the manu- facture of various kinds of glass. Amongst these, miners’ lamp glasses have received attention owing to a suggestion of the Home Office. A summary of the results arrived at, so far as the work has gone, is given in Nature, April 15. The Glass Research Committee have had analyses of various industrial glasses made by Mr. Bertram Blount, Mr. W. C. Hancock and Mr. Otto Hehner. The rest of the work has been carried out mainly at King’s College by Prof. Herbert Jackson and Mr. T. R. ‘ Merton. This work has involved a detailed study of the chemistry of silicates, aluminates, borate^, &c., in their relation to glass manufacture. A large number of experimental melts have been made, and the formulas now issued have been thoroughly tested as to their suitability for the purpose required. It might perhaps be thought that the chemical analyses them- selves would be a sufficient guide for manufacturers. This, however, is not the case for several reasons. It was found that mixtures made in accordance with analytical results alone were not always satisfactory. There are certain other factors, such as the temperature of the furnace, the action of the mixtures on the clay crucibles during fusion, and also the influence of certain volatile products to facilitate the incorporation of the ingredients. The following formulas for miners’ lamp glasses are given :— Miners’ Lamp Glasses. Parts. (a) Sand ............................... 65'0 Alumina (A12O3) ..................... 1’0 Calcium corbonate ................... 0*6 Arsenious oxide (As2O3) ............. 2*0 Antimony oxide (Sb2O3) ............. 1*0 Potassium nitrate ................... 3*0 Sodium carbonate (Na2€03) ......... 14*0 Boric anhydride (B2O3)........' .... 24*0 A colourless and fusible gla s withstanding rapid cha of temperature exceptionally well. T'aT’T'Q (5) Sand................................. 65*0 ’ Alumina (A12O3) ....................... 1*0 Calcium carbonate ..................... 0*6 Arsenious oxide (As2O3) ............... 2*0 Antimony oxide (Sb2O3) 1*0 Potassium nitrate ..................... 3*0 Anhydrous borax (Na2B4O7).......... 26*68 Boric anhydride (B2O3)............... 5*5 (b) is the same glass as (a), but the ingredients have been varied to avoid the use of so much boric anhydride, which is at present apparently difficult to obtain on a commercial scale. It will be noted that nothing has yet apparently been done with regard to the question of annealing, the importance of which is suggested by the recent work of the National Physical Laboratory already recorded in these columns. Load Factors and Power Factors. In a pappr read before the American Institute of Electrical Engineers, W. Sykes and G. Bright give the following table, showing the various load factors and power factors in a mining installation and the ways in which they may be improved :— Load. Load factor per cent. Method of improvement. Power factor per cent. Method of improvement. Haulage Hoisting Ventilation Coal-cutting Pumping Tipple or breakt r Machine shop ) Blacksmith shop ) Lights 15 to 30 10 to 30 100 20 to 50 70 to 100 20 to 60 40 to 70 60 to 90 Proper arrangement of schedule. Equalising system Do cutting at night to im- proveloadfactor of system. If p ssible change part of pumping to night turn. Keep output steady ( Load too small to affect load ) (. factor seriously. ) Load too small to affect load factor seriously. 70 to 100 60 to 90 70 to 90 70 to 100 70 to ICO 50 to 70 Use of synchronous motor-generator sets or synchronous converters. Equalising system. Use special winding to give high power factor at light loads. Use synchronous motor-generator sets or synchronous converters. Use synchronous motor-generator sets or synchronous converters. Use motors of proper capacity—not too large. (Use of motors of proper capacity—not ( too large. If alternating current, use transformers of proper capacity—not too large. The Generation v. the Purchase of Power. A question which has often agitated the colliery owner who contemplates electrification is that of deciding as to the respective merits of a self-contained system of generation and of use of power from a central supply system. It is a question that has to be determined by the peculiar circumstances of each undertaking, such as the cost of current and the purpose for which it is required, the loads given by some machines, such as pumps, being much better than others, such as winding engines. With this qualification, some figures put forward by the Westinghouse Electric and Manu- facturing Company—the American company—are of much interest. A method is given of obtaining the cost of power at an average coal mine with its own plant, and a comparison made with the cost where central station energy is purchased at a definite rate per kw.- hour. The equipment taken consists of four return tubular boilers, two boiler feed pumps, one deep-well pump, one feed-water heater, one double-balanced steam winder (400-horse power maximum), one fan (5-horse power), two high-speed 150-horse power engines for generators, two 100-kw. 500-volt direct-current belted generators, one 10-horse power engine for machine shop, one ditto for screen, one 25-horse power engine for elevator, one 5-horse power engine for coal conveyor to boiler-house, two steam pumps at shaft bottom (each 10-horse power); the motors operated from the generator have a combined capacity of 500-horse power ; the mine has an average output of 1,100 tons per day, and operates an average of 18 days per month all the year round, but one of the generators runs continuously. The first thing to do is to arrive at the load factor, and this should be taken as the ratio of the average load to the total 5 min. or some other short time peak, rather than on the capacity of existing machines. In this way the capacity in kw. hours of each machine if it works 24 hours may be arrived at, as well as the actual kw. hours during the same period; the ratio gives the load factor for a 24-hour working day. The capacity in kw. hours for 30 full days may then be compared with the actual kw. hours, made up of the actual kw. hours for 18 working days plus the kw. hours for 12 non- working days; the ratio gives the load factor for 30 days. This depends largely on the amount of fan and pump load, and may vary from 13 to 40 per cent. In the case examined the figures are as follow :— Twenty-four Thirty hours. days. Capacity in kw. hours ..... 8,?32 ... 246,960 Actual kw. hour............ 2,184 ... 50,640 Load factor.......Per cent. 26 6 ... 20 6 In estimating the possible economies when power is purchased, the following items of first cost are taken:— Boiler installations, 5,400 dols.; boiler house, 2,000 dels.; engines. 6,s00 dols.; engine house, etc., 2,500 dols.; piping, 1,500 dols.; generator, switchboard and wiring, 2,640 dols. The interest, depreciation, repairs and upkeep may then be estimated for each portion of the plant, and this, together with the difference in the cost of labour, insurances, etc., will represent the saving, no saving, however, being estimated on the engine building, since it would probably be used to house the new motor generaterand switchboard. In the case taken the total cost per 30 days is calculated as 1,165*45 dots.—284*40 dols. being fixed charges and 88105 dols. operating expenses—and the saving 900 25 dols. Since the total of kw. hours per month is 50,640, the total cost of power per kw. hour is 0 023 doh, and the saving will be 0*0178 dol. The difference, or 0*0052 doh, is the common cost per kw. hour, which will exist in either case. The total cost of the new equipment, which must be purchased in order to utilise central station energy, is given as 8,790 dols., and, as an offset, it is estimated that the old plant will fetch 2,045 dols.; the net cost, theie- fore, will be 6,745 dols. . Interest, depreciation, upkeep and repairs on the new plant will amount to'71*00 dols. per month, or 0*0014 dol. per kw. hour. Adding the common cost, we have 0 0066 dol. as the total cost per kw. hour, excluding the charge for current. If this value be subtracted from the total cost of 0*023 dol.,® 0*0164 dol. is obtained as the limit charge for current that would justify the.change. The above figures apply actually to American conditions, but the same methods of calculation can be used under any conditions that may present themselves. Safety Lamp Glasses from America. According to Mr. J. W. Paul, of the United States Bureau of Mines, efforts are now being made to manu- facture in that country numerous appliances used in the illumination of mines that have hitherto been imported. “ At the time of the organisation of the Bureau of Mines,” says Mr. Paul, “ there was not offered by any American concern lamps other than oil burning lamps of the Clanny type. In 1909, Congress admitted miners’ safety lamps free of importation duty. Within the past year the patents on certain foreign types of lamps have expired, and there are now being placed on the market two ‘made in America,’ naphtha burning, internal ignition, miners’ safety lamps conforming in every particular to the Wolf lamp. Through the agency of the Bureau there have also been developed types of miners’ permissible electric lamps, which are now being manufactured and placed on the market in competition with electric permissible lamps manu- factured abroad.” Mr. Paul makes a further inteiesting statement:;—“The highest type of glass chimneys for miners’ safety lamj s used in foreign mines have hereto- fore come from Germany, but owing to the present war in Europe the collieries in England are unable to procure at home the quality of glass chimneys previously obtained from Germany. This has resulted in there having been recently placed in America orders for many thousand safety lamp glasses ‘ made in America, for use in England.’ ” It would be noted that the latest Safety Lamp Order issued by the Home Office contains specifications of American glasses. H-Beams for Mine Timbering. One of the pioneers in the use of steel for timbering in the United States was the Carnegie Steel Company, and in 1914 this company alone furnished to the mines sufficient plain and fabricated beams for inside mine work to timber permanently 14 miles of main headings, in addition to 700 props, In the anthracite region the usual form employed is a three-piece set, consisting of two H-beam legs and an I-beam collar ; the H beam has now largely displaced the earlier forms of leg sections. The Carnegie Steel Company in 1914 supplied 3,845 of these sets, as compared with 190 in 1907 and 750 in 1909. TRADE AND THE WAR. Export Licences—Germany and Goal for Sweden—Labour in War Factories—L.G.G. and its Goal—House Goal in Scotland. Arrangements have been made by the Board of Trade that contraband goods and goods on the prohibited list, for which export licences have been duly granted, may be shipped to Holland by vessels of any of the under- mentioned British companies, provided they are consigned to the Netherlands Oversea Trust:—Bristol Steam Naviga- tion Company, Cork Steamship Company, General Steam Navigation Company, George Gibson and Company, Great Eastern Railway Company, Hull and Netherlands Steam- ship Company, James Rankine and Son, W. Swanston and Sons, and the Tyne-Tees Steam Shipping Company. It is announced from Stockholm that all ships for Scandinavian ports with coal from England which sailed before learning of the new German contraband regulations of the 18th inst. will be permitted to pass through the sound if the Swedish Foreign Ministry receives a report giving the name of .the ship, her owners, and her destina- tion, and a declaration that the new regulations were unknown to her at the time of leaving England. A supplement to the London Gazette contains the text of a new regulation under the Defence of the Realm Acts with regard to obtaining labour for factories engaged in the production of war supplies. The new regulation is as follows:—The occupier of a factory or workshop, the business carried on in which consists wholly or mainly in engineering, shipbuilding, or the production of arms, ammunition, or explosives, or of substances required for the production thereof, shall not, nor shall any person on behalf of the occupier of such a factory or workshop, either directly or indirectly, by canvassing, advertisement, or otherwise, take any steps with a view to inducing (a) any person employed in any other factory or workshop being a person engaged on work for any Government department or otherwise serving war purposes to leave his employment, or, (6) any person, resident in the United Kingdom at a distance of more than 10 miles from the occupier’s factory or workshop, to accept employment therein otherwise than by notifying vacancies to a Board of Trade Labour Exchange, and in the event of any person contravening the provisions of this regulation he shall be guilty of an offence against these regulations. The Public Control Committee of the London County Council, reporting upon the sale of coal says“ In consequence of the present high prices of coal and the hardship caused thereby to persons of limited means, we have had under consideration the question of taking special steps to safeguard the interests of consumers, especially those resident in poorer districts where coal is generally sold by hawkers in small quantities. The practice of hawkers who sell coal in the streets in advertising their prices varies. In some cases a metal tablet is exhibited indicating the price; in others, a tablet is shown on which the figure “ 1,” representing Is., is permanently marked, the figures denoting the pence being marked in chalk and altered as required ; while in some instances no price at all is indicated. In the absence of any effective regulation, instances have been found in which, hawkers vary the price from the authorised price fixed by the coal merchant. In many cases the price is increased in the poorer localities as in these districts the purchaser is more dependent upon the trolley man for his supplies, and in view of the consequently increased demand the carman is able to increase his price. Cases have also been found in which, in order to obtain a larger order, e.g., 5 cwt., a trolleyman will be willing to sell his coal at Id. a cwt. less than his advertised price, recouping himself by increasing the price of single hundredweights. In this way he is frequently able to dispose of his stock more rapidly without any pecuniary loss to himself. While it is true that trolley- men have a regular round and regular customers, and it is therefore in many cases not to their interest to increase prices, nevertheless it is usually at the expense of the casual purchaser that the trolleyman is able to make an illegitimate profit. Although there is no evidence that the practice is widely prevalent at the present time, we are of opinion that the absence of effective regulation undoubtedly enables irregularities to be committed which should be suppressed, and we consider it very desirable that the Council should possess the necessary powers to enable it to deal with the matter. We are advised that the best method of effecting the object in view is to make additional by-laws under the Weights and Measures Act, 1889, (i) prescribing the affixing of metal tablets containing the price of coal on vehicles carrying coal for sale, and (ii) prescribing that coal shall not be sold at a greater price than the price shown on such tablets. The steamer “ Mobile ” which left Barry Dock last week laden with Welsh coal has been sunk by a German submarine about 40 miles westwards of Lewis. The English collier “Fulgent” was also torpedoed off the Blasket Islands last week. It is reported that the Swedish War Insurance has refused to insure ships with pit props for England, fearing that the Germans will capture them while passing through the Baltic. The Danish insurance authorities, however, are accepting risk, many Swedish and Danish ships laden with props from Falkenburg for England having lately been insured. At the meeting of the L.C.C. on Tuesday the new by- laws recommended were agreed to without opposition and without a word of discussion. Reporting upon contracts the Finance Committee of the Hammersmith Borough Council states on March 17 last the council accepted the tender of Messrs. G. Hinchliffe and Co.,, of 5, Lloyds-avenue, E.C., for the supply of house coals, the chief items being—Wrallsend, .£1 7s.; London brights,