December 6, 1918. THE COLLIERY GUARDIAN 1189 The power factor 0-55 corresponds to a lag of 56| degs., that for 0-75 corresponds to 41| degs., that for 0*8 corresponds to 37 degs., and that for 0-998 corre- sponds to 3 degs. By trigonometry, as before we find ON = OP cosine PON; that is to say, ON = 185 x 0’55, = 101 75. Similarly, PN, = PP15 cosine P PNX, = 152 x 0*75 = 114. PxN2 = P1P2, cosine P2P1N2 = 132 x 0’8 = 105’6. The useful input of P2P< will equal 94 x cosine 3° = 94 x 0 998 = 92’8. The total useful input, therefore, of the four groups of machines represented by the different lines OP., etc., is 414T5 kilo-volt-amperes. From a table of sines we can obtain the values of PN, P1N1, having the values of the different angles of lag. PN = OP sine PON = 185 x 0 835 = 154 5. P1N1 = PPt sine 41J° = 152 x 0’663 = 100’8. P2N2 = P.P, sine 37° = 132 x 0’6 = 79’2. The wattless energy corresponding to P2P3, = P2P3 sine 3° = 94 x 0 052 = 4’89. The total wattless energy, therefore, is 154*5 + 100’8 4- 79’2 + 4’89 = 339 39. We can now find the resultant angle of lag P3ON6 ; its tangent equals = 0’819 = tangent of 39b°. This, therefore, is the resultant angle of lag; and the cosine of the same angle is 0’77 : which is the resultant power factor. The resultant apparent input OP3 may be found as before. It equals ON6 secant P30N6, =. 414 15 x 1'57 = 650 kilo-volt-amperes. As mentioned above, the writer, in this example, has taken for the different quantities figures that are likely to occur in actual practice. It would be very rarely that the power factor of one or more rotary converters would be exactly 1-0, though it might easily be the figure given above, or, again, it might easily be the same figure leading. SAFETY LAMPS CLASSES ORDER. The Home Secretary’s Order, to which reference was made in our issue of November 8, states that glasses manufactured by the manufacturers named in the schedule to this Order and bearing the manufacturer’s trade mark are approved, until further Order, for use in any flame safety lamp of approved type. The approval is subject in each case to the conditions set out in the schedule and to any condition specified in the official description of the lamp in which the glass is to be used. All provisions relating to the approval of safety lamp glasses contained in previous Orders under section 33 of the Act, and the Order of Novem- ber 6, 1914, made under the same section allowing temporarily the use of unapproved glasses, are revoked. Provided that unapproved glasses which are at present in use may continue to be used until March 31, 1919, if they comply with the requirements as regards dimen- sions and otherwise specified in the official description of the lamp in which they are used. SCHEDULE. Manufa cturers. 1. Messrs. Ackroyd and Best, Limited, Morley, near Leeds. 2. Messrs. Butterworth Brothers, Limited, Newton Heath, Manchester. Trade Mark of Glass. ■ HAILUXO” 3. The Macbeth-Evans GIass Company, Pittsburgh. U.S.A. MACBETH No. 2100 HIGH SPEED 4. Messrs. John Moncrieff, Limited, Perth. 5. The Pittsburgh Lamp, Brass and Glass Company, Pitts- burgh, U.S.A. 6. Messrs. Stevens & Williams, Limited, Brierley Hill,near Stourbridge. Conditions. (а) That in addition to bearing the trade mark each glass is marked to show its size, either (i.) by a numeral following a lampmaker’s initials as specified in the official description of the lamp in which’ the glass is to be used, or (ii.) (for cylindrical glasses only) by numerals giving the maximum external diameter and mean height of the size (the former to be placed first). (б) That in any size of glass the variations in external diameter and height do not exceed ? mm* and ± 4 mm. respectively, and that in any one glass the variation in thickness does not exceed 1mm. (c) That the ends of the glasses are not out of parallel to an extent of more than 4 mm. (d) That the glasses are of the same composition and quality as the samples officially tested. Release of Miners to be 5,000 per Day______As the result of urgent representations made to the Coal Controller, a large flow of miners will shortly be returned to the collieries from the Army. The total number so returned before the end of January is estimated at 100,000. It is anticipated that by about the middle of December 5,000 per day will be released. Steps are also being taken with a view to the early demobilisation of pivotal men in the coal industry. SOUTH WALES INSTITUTE OF ENGINEERS. The ordinary general meeting of the South Wales Institute of Engineers was held at Cardiff on Friday, November 29, Mr. J. Fox Tallis, the president, in the chair. The following office bearers were elected: Vice- presidents: Mr. J. Dyer Lewis, H.M.I.M., Mr. D. E. Roberts, M.Inst.C.E., Mr. W. A. Chamen, M.Inst.E.E. Members of council: Messrs. W. Johnson, Bridgend; T. Sugden, London; B. Nicholas, Pontypool; J. W. Hutchinson, Tondu; C. A. Seyler, B.Sc., F.I.C., Swansea; J. C. Davies, Gowerton; E. L. Hann, Aberaman; H. R. Jones, Dowlais. The following were elected to the institute:—As members: Messrs. J. D. Davies, Cwmpennar, Mountain Ash; W. R. Hann, Cardiff; E. H. Hutchin- son, Manchester; A. S. Little, Porthcawl; R. A. Lewis, Ebbw Vale ; W. Morgan, Llantrissant; T. H. Naylor, Manchester; J. Nicholas, Tumble, Llanelly; I. Rees, Llantwit Fardre; L. A. Snow, Dynas Powis; E. J. Thomas, Abercarn; E. G. Weddell, Bridgend; M. Williams, Gwauncaegurwen. As associate members: Messrs. A. Jenkins, Cardiff; G. Stainer- Johnson, Ely, near Cardiff; W. E. Milliam, Bridgend. Gas Power v. Steam Power. Arising out of remarks previously made during a discussion on gas-firing boilers, the subject of a paper by Mr. T. M. Hunter (Colliery Guardian, May 31, 1918, p. 1097), Mr. T. Sugden said although in theory the gas engine should show the most economical results, and undoubtedly does, yet difficulties arise in actual working which more than counterbalance in the long run any economical advantage over steam plant, owing to the greater reliability of the steam engine. The insurance companies have found the insurance of gas engines an unprofitable business. The progress made in connection with gas engines has been more in the direction of high-speed multi-cylinder vertical gas engines, which give better results on the whole, more particularly in connection with blast furnace gases, than the large low-speed horizontal gas engines. In determining whether gas or steam plant should be used, it would be well to keep in mind the following points: The gas engine is not so reliable as the steam engine, and it is much more costly in upkeep and repairs. A much larger space is required for the same power developed for gas engines than for steam tur- bines.. In some industries steam is used for other purposes than power; in such cases steam plant is preferable. Water used for cooling the cylinders of gas engines which contain deposits involves costly repairs, owing to cracks developing. Failure of piston lubrication causes “ seizing ” of the pistons and serious breakdowns. Unless a special attendant in charge of the gas engine is available, it is a great source of anxiety, owing to frequent stoppages and breakdowns. Mr. W. O’Connor, F.G.S., said the paper was well timed, seeing the strong probability of a greater pro- duction of gas from coal in the immediate future and its possible use for the prqduction of power by various means after the extraction of the many valu- able by-products contained in the original gas. Where the gas used for firing boilers was a waste or surplus product of this or other industrial opera- tions, or supplied from a well or other natural source, the condition contemplated by the author of the paper would no doubt be realised; but where the gas had to be produced from a solid fuel (and that probably a low-grade one), this attractive condition as to capital cost would not apply. As to the ad- vantage of gas fuel producing no soot on economiser tubes or other surfaces, this has been a tangible -con- sideration ; but recent researches into the combustion of coal in boiler furnaces had shown that the pro- duction of soot was not inevitable when the phe- nomena of combustion are initiated under favourable conditions of air supply and allowed sufficient space and time to carry on to a degree of completion before the temperature of gases is reduced below that neces- sary for complete combination. Mr. Halbaum said the success of firing boilers with coal tar by-product was not yet established,, and ’he advised a suspension of judgment until certain experiments of which he had cognisance were completed. The discussion was closed with a vote of thanks to Mr. Hunter. A Modern Colliery. Continuing the discussion of this paper, (by the late Mr. George Hann) (Colliery Guardian, July 26, 1918, p. 173), Mr. Hugh Bramwell said he quite agreed that the setting. up of a big central station for generating electrical power for a group of collieries was the most economical method, and he thought in putting forward reasons for this contention Mr. Hann had under-estimated rather than over-estimated his case. Nevertheless, he had approached certain factors in a slightly wrong way. For instance, he had com- pared the unit of electricity in the one case with the pound of coal used under the boilers in the other. In a unit of electricity there were a number of items of cost other than merely coal used. As a matter of fact, the comparison should have been between the value of the unit of electricity and the value of the pound of steam. The value of a unit of electricity could be made greater use of than the value of a pound of steam. Electrical motors were more efficient machines in the use of their power than were steam engines in the use of steam—i.e., generalising. The discussion was further adjourned. The Draper Coal Washer. Prof George Knox, F.G.S., M.Inst.M.E., dis- played on the lantern screen a series of plates illus- trating the evolution of mineral washing machines, explaining their features, and making a more.detailed statement on the Draper Coal Washing ^machine (see p. 1186). Discussion. Mr. Draper said the entire cost worked out at l-5d. per ton of washed coal on the present low output at Llwynypia, due to shortage of material. This figure included cost of current and labour. There had been no cost of upkeep after a 12 months run. He (Mr. Draper) hoped to give a supplementary paper on the subject at the next meeting. Replying to the presi- dent, Mr. Draper added that, speaking from memory, the quantity of ash in the fine dust of the mesh was from 18 to 25 per cent., and it washed down to about 5-5 per cent, and 6 per cent. In proposing a vote of thanks to Prof. Knox, the President predicted a great success for the Draper coal washer. The discussion was adjourned. CLINKER AND ASH IN FUEL. In a letter to The Times Engineering Supplement, Mr. D. Brownlie gives the results of complete investi- gations into 250 different steam boiler plants, repre- senting 27 different industries, and comprising a total of 1,000 boilers with an aggregate annual coal bill of 2,166,000 tons. The figures for the coal analysis before and during the war are tabulated as follows, arranged in divisions corresponding to the percentage of ash. These figures include a few samples of coke and coke breeze, but this will not affect the general results. Before the War. (1910 to end of July 1914.) No. of boiler plants tested. Per cent, of plants. Average ash in coal. Per cent. Average heating value in coal. B.Th.U. 13 21’7 .... 0-5 13,450 13 . 21’7 .... 5 - 74 . 13,330 14 23’3 .... 7| 10 . 12,750 7 11’6 .... 10 -124 • 12,760 10 16’7 w... .. ' 12|-15 . 12,100 3 5’0 .... 15 -20 11,500 0 nil over 20 nil Total 60 Since the War. (End of July 1914 to present time.) 5 ... 2’6 .... 0-5 12,750 17 ... 8’9 .... 5 - 7i 12,600 38 ... ... 20’0 .... 74-10 12,410 41 ... ... 23’2 .... 10 -124 11,835 35 ... ... 18’4 .... 134-15 .... 11,400 24 ... ... 12’7 .... 15-20 .... 10,550 27 ... ... 14’2 .... over 20 9,720 Total 190 According to these figures there has been a decided fall in the quality of the coal. Thus, before the war only 21-7 per cent, of the coal used contained 12 per cent, or over of ash, whereas during the war the figure is 45-3 per cent. At the present time the average heating value is probably at least 10 per cent, inferior to pre-war days. MAXIMUM PRICES FOR FRENCH COALS. The French Ministry of Munitions has notified the following increases above the prices mentioned in our issues of May 10 (p. 943), July 26 (p. 186), and November 1 (p. 914) last:— Saint-Etienne Basin. Mines du Gros, 6fr.; Soc. anon, des Houilleres de Saint-Etienne, 8 fr.; Soc. anon, des Mines de la Loire, 8 fr.; Soc. anon, des Houilleres de Montrambert et la Beraudiere, 6fr.; Soc. anon, des Houilleres de Saint- Chamond, 6’95 fr.; Cie. des Mines de Roche-la-Moliere et Firminy, 6 fr.; Cie. des Mines de Villeboeuf. 10 fr.; Houilleres de la Chazotte (Cie. des Chemins de fer Paris-Lyon-Mediterranee), 4 55 fr. Rive-de-Gier Basin. Soc. anon, des Mines de la Hauie-Cappe, 10 fr.; Cie. des Mines de la Peronniere: Coal, 6’60 fr.; briquettes, 12’70 fr. Marseilles District. Soc. Nouvelle des Charbonnages des Bouches-du- Rhone, 6 fr. These prices operate as from October 16 last. If necessary, separate prices 'will be fixed for each colliery, according to the commercial quality, size and ash content of the various coals and to the desirability of increasing the output of any special grade. REVISED FREIGHT RATES. The Mission Francaise des Charbons, London, has issued a revised list of freight rates foi British and Allied vessels conveying coal to French ports. The rates fixed by the Limitation of Freights (French Ports) Amendment Order, No. 504, dated May 1, 1918 (made by the Shipping Controller, and reproduced in our issue of May 17), remain in force with the following exceptions:— The maximum rate for steamers not exceeding 400 tons gross register carrying coal to French ports is 6s. less than the old schedule, exclusive of cost of war risk insurance on ship. For steamers above 400 tons gross register no altera- tion has been made. For sailing vessels fully rigged or dismantled, or barges, the rates are 30s. less, exclusive of cost of war risk insurance on the vessel. The alterations operate from December 1. Oil from Shale in Sweden.—A report from Sweden states that works have been established at Lamma in Hidinge, Kirchspiel, Nerika, for the extraction of oil from shale, a practically inexhaustible source in that locality. Pro- duction is to be begun at once. This factory will treat 30,000 tons of shale annually. As the shale yields 4 per cent, of oil, the output of oil will be 1,200 tons.