THE COLLIERY GUARDIAN. 73 July 12, 1918. ________________________________________________________________________________________________________________________________________________________________ pendently of all switchgear, i.e., direct to the mains. One terminal of each secondary should be earthed, while the other should be connected to two lamps in parallel, one side of which should be also earthed. This is shown in fig 16. The lamps being in parallel, one can burn out without destroying the indication that current is “ on ” ; but a damaged lamp should always be replaced immediately, so as to remove the lisk of both series of lamps becoming out of order. Fig. 15 shows a similar arrangement, but the trans- formers on each section are connected in parallel by running a single pilot wire between the sub-stations. With such a connection, should the fuses blow on one transformer, instead of the indicating lamps failing, as would be the case in fig. 16, the lamps would still remain alight, receiving their current from the trans- former at the other end of the section through the pilot wire. Where the transmission is by overhead cables, the pilot could easily be run on the same poles. As regards working on the bus bars at the sub-stations a pilot lamp could be provided also by a transformer, but usually the voltmeter could be relied upon as a check. From figs. 16 and 17, however, it will be obvious that, where work has to be carried out on sub-station bus bars, the section of main can be completely isolated at the nearest sub-station on either side. The pilots on the mains would indicate all clear apart from any bus bar indication. Oil switches could be examined by opening the isolating switches on each end of a given section, the pilot lamps always acting as a check. General. It has been assumed that in all the cases dealt with above, the isolating arrangements were apart from the handles operating the circuit breakers, and situated below in suitable cells. There are, however, many boards in use of the pillar type which provide an isolating arrangement by with- drawing the switches on suitable slides. It will be obvious that special isolating lamps are unnecessary in such cases, and when providing for pillar-switch pilots the isolating pilots will of course be excluded from the diagrams. It may occur to some that where a number of lamps are in series in a constant-current circuit, it may be difficult to trace which lamp is defective when all lights go out. Usually the switches for pilots would be fixed outside the switch cases and should be easily got at, the design being of the simplest form. It will generally be an easy matter, should a lamp burn out, to close the switches by hand one by one, until a switch short- circuits the lamp which has burnt out, whereupon the lamps will all light up. Labelling.—Too much emphasis cannot be placed upon the importance of distinctly labelling all switches and isolators, and especially the latter where they are below the operating platform. Confusion may easily arise from the fact that when facing the switch handles on the operating platform, flowing through the primary turns may reach a value sufficient to give a dangerous shock. It is therefore advisable, when working on meters or other apparatus necessitating the disconnecting of a current transformer secondary, to short-circuit the coil temporarily until the work is complete if the primary is carrying current. Another effect of an open circuit on a live current transformer secondary is to cause the iron circuit to become hot—due to the heavy flux it is called upon to carry, when the secondary current is not present to neutralise its effect. ________________ MINING EMPLOYMENT STATISTICS. The Board of Trade Labour Gazette for June states that employment in coal mining continued good during May. There was a decrease of 14,014 (or 2*6 per cent.) in the number of workpeople employed at collieries making returns, as compared with a month ago, and a decrease of 22,220 (or 4T per cent.) on a year ago Of the 517,856 workpeople included in the returns for May, 271,590 (or 52’4 per cent.) were employed at pits working 12 days during the fortnight to which the returns relate; a further 185,687 (or 35’9 per cent.) were employed at pits working 11 but less than 12 days. Districts. Work- people em- ployed in May 1918* Average No. of days worked per week by the collieries in fort- night ended Inc. ( +) or dec. (—) in May 1918 on a Districts. Average No. of days worked per Work- week by mines people in fortnight em- ended ployed (--------A-------v in May May Apr. May 1918 * 18, 27, 26, 1918. 1918. 19] 7. Inc. (+) or dec. (—) in May 1918 on a ________ Month Year ago. ago. Days. Days. Days. Days. Days. Cleveland............ 7,475 ...5’98...5’99...5’94...-0'01... +0’04 Cumberland and Lancashire ....... 5,884 ...6 00.. 6’00...5’98... — ...+0’02 Scotland ............ 660 ...6'00...5'58...5’59... + 0’42...+0’41 Other districts .... 4,439 ...5’89.5'85...5’97...+0'04...-0’08 Total ...... 18,458 ...5’96...5'94.5'94... +0’02... +0’02 * At mines included in the returns. Shale.—The returns show that 5,059 workpeople were employed in the fortnight ended May 18,1918, compared with 5,142 workpeople in April, and with 4,911 in May 1917, at mines which worked six days in each period. Pig Iron Industry.—Employment continued good during May. The decline in the number of furnaces in blast was due to a dispute in South Wales. 'England Wales. Northumberland ... Durham ........ Cumberland ..... South Yorkshire ... West Yorkshire... Lancs. & Cheshire... Derbyshire ....... Notts and Leicester Staffordshire ..... W ar wick, W orcester and Salop....... Glo'ster & Somerset North Wales ..... South Wales & Mon. ’fr A27r- 1918. 1918. 1917. ago' ag0’ Days. Days. Days. Days. Days. 31.213.. .5’49...5’46...4'89...+0'03...+0'60 84.776.. .5'50...5’45...5’05... + 0'05... +0’45 5,201...5'37...5’78...5'88...—0’41...—0’51 62.379.. .5'79...5 91...5’90...—0’12...—0'11 24.747.. .5’47...5’72...5’83 ..-0’25 -0’36 49.451.. .5'84...5'92...5'92...-0’08...-0'08 33.338.. .5'85...5’80...5’84...+0’05...+0 01 33.934.. .5’64...5’60...5’68... +- 0’01...-0'04 26.147.. .5'86...5’88...5’88...-0’02...-0'02 6.893.. .5'88...5’84...5’87... +0’04... +0'01 4,081...5'96...5'96...5’83... — ... +0'13 6.994.. 6 00...5'94...5'85 +0'06... +0'15 103,330...5'66 .5’89...5’83... -0’23..—0'17 Total ...... 472,484...5'68.5’75...5’64...—0'07...+0'04 Scotland. West Scotland ____ 20,541 5’51...5 43...4 93 ... 4- 0’08... + 0'58 The Lothians ...... 1,822 5'54 ..5'55 ..5'32...—0'01... +0'22 Fife ............... 22,542 . 5'62...5'55...4'34...+0’07... +1'28 Total ...... 44,905...5’57...5’50...4'64...+0'07... +0'93 Ireland ........... 467...5'12...5'20...4'77...-0’08...+0'35 Total, U.K______ 517,856 ..5’66...5’73...5’55...-0'07...+ 0'11 * At the collieries included in the table. The following table shows the numbers employed and the average number of days worked, distributed accord- ' Districts. No. of furnaces, included in the returns, in blast at end of A Inc. (+) or dec. (-) in May 1918 on a A * Month May Apr. May Year England ft Wales: 1918. 1918. 1917. ago. ago. Cleveland 76 ... 75 ... 78 ... + 1... - 2 Cumberland & Lancs. 34 ... 34 ... 34 — — S. and S. W. Yorks ... 12 ... 12 ... 13 — — 1 Derby & Nottingham... Leicester, Lincoln and 34 ... 34 ... 30 ... — ... + 4 Northampton 30 ... 30 ... 27 — + 3 Staffs and Worcester... 30 ... 30 ... 30 — S. Wales & Monmouth 7 ... 13 ... 11 - 6.’’ - 4 Other districts 4 ... 4 ... 5 ... —... - 1 227 ... 232 . . 228 ... - 5... - 1 Scotland 67 ... 65 ... 70 ... + 2... - 3 Total, U.K 294 ... 297 ... 298 ... - 3... - 4 'n, 41 H Jtgo VouT S U^-PI-Y Fig. 16. it 0 iu 3 0 a. 1 trt fl! 3 K Fig. 17. the panels read from left to right, but when one gets below and faces the isolating panels, they may read from right to left, i.e., in the opposite direction, depending on the construction of the board. Current Transformers.—In conclusion, the writer would point out a danger in connection with current transformers which, although not new, may not be generally appreciated. On all high-tension boards, it is necessary to use current transformers in connection with trip gear, ammeters, and the current coils of various other meters, in order to avoid bringing the high voltage to the meters. A current transformer usually consists of one or more turns of the main current-carrying circuit around an iron core. A secondary circuit of fine wire is also provided, which supplies the current for the current coils of the meters, etc. These secondary coils usually supply all the current coils connected in series, but may be short-circuited upon themselves without damage. This is due to the fact that the flux produced in the iron circuit is limited by the current passing through the primary turns, and as the short-circuit current produced in the secondary winding is sufficient to neutralise the primary flux without an abnormal current flowing, there is no danger in short-circuiting the coil. The danger lies in leaving the secondary circuit open when the primary is alive, as the potential across the terminals on open circuit when a heavy current is ing to the principal kind of coal raised at pits at which the workpeople were engaged:— Average No. of days worked per Inc. (+) or Work- week by the pits dec. ( — )in people in fortnight May 1918 em- ended on a ofeoal. ployed ,-------------------( t.-----------( in May May Apl. May Month year 1918 * 18, 27, 26, *®ar 1918. 1918. 1917. ag0’ ag0* 11710. 1*710. 1*71<. Days. Days. Days. Days. Days. Anthracite ......... 5,531 .5'71...5'05...4’69...+0'66...+1’02 Coking ............. 25,040...5’78...5 81...5 73...-0 03...+0'05 Gas.................. 32,170...5'27...5’39...4’86...—0’12... +0’41 House................ 48,715...5'71...5’72 ..5'71..—0 01... — Steam................ 182,232...5’65...5’80...5 66...-0’15...—0’01 Mixed................ 224,168...5'71...5’73...5’53...-0’02... +0’18 _______ _______ All descriptions ... 517,856...5’66...5’73...5’55...-0’07 . +0’11 * At the collieries included in the table. Iron. Shale, and Other Mining.—Employment con- tinued very good at iron and shale mines. Returns received for each of the three periods named below, relating to the same mines and open works in each case, show that 18,458 workpeople were employed at mines included in these returns in May 1918, a decrease of 159 (or 0'9 per cent.) on the previous month, and an increase of 1,513 (or 8’9 per cent.) on a year ago. Iron and Steel Works.—Employment at iron and steel works continued very good, and showed an improve- ment on a year ago. Shortage of labour was again reported from every district. According to returns relating to 118,114 workpeople, the number of shifts worked during the week ended May 18, 1918, was 678,597, showing a decrease of 887 (or 0’1 per cent.) on a month ago, and an increase of 33,483 (or 5’2 per cent.) on a year ago. Engineering Trades.—These trades continued to be extremely busy during May, and a great amount of overtime was worked. Trade unions with 330,471 members (mostly in skilled occupations) reported 0’1 per cent, unemployed at the end of May, compared witfi 0’1 per cent, a month ago and a year ago. Tin-plate and Steel and Galvanised Sheet Trade. — The number of tin plate mills working at the end of May showed no change from a month ago, but an increase of 21 on a year ago. Shortage of labour and difficulties in securing supplies of raw materials were reported. The number of mills making steel and gal- vanised sheets working at the end of May showed a decrease of four as compared with the previous month. Compared with a year ago there was no change. Nut, Bolts, Nails, etc.—Employment with nut and bolt makers and with shoe rivet and wire nail makers con- tinued very good. Tubes.—Employment continued good at Birmingham, Wednesbury and in South Wales and Monmouthshire. Wire.—Employment continued good in most districts. Wages.—The changes for which particulars are avail- able show that during the five months, January-May, 21.500 persons engaged in coal mining received a net increase amounting to £500 per week. Other net weekly increases:— Iron and other mining, 8,000 workers,’’ £2,200; pig iron manufacturing, 32,000 workers, £6,100; and iron and steel manufacturing, 57.500 workers, £18,800. Prices and Wages.—The results of recent ascertain- ments of the selling prices of coal and iron are given below:— Prices according to Inc. (+) or dec. (—) last audit. of last audit on ______________ Product and Period Average district. covered hv sellin& Previous A year last audit aUdit’ per ton. Coal. 1918. s. d. s. d. s. d. Average of all classes of coal at pit’s mouth.) Durham........ Jan.-Mar. ... 18 lj...— 0 0|...+ 2 6| Manufactured Iron. North of England Mar.-Apl. ...281 9|...+ 5 2 ...+ 12 91 (Rails, plates, bars and angles.) Midlands ...... Mar.-Apl. ...313 7|... + 1 4 ... + 8 8 (Bars, angles, tees, sheets, plates, hoops, strips, etc.) West of Scotland Mar.-Apl. ...296 4J... + 1 2 ...+ 9 5f (Round*, squares, flats, tees, angles, hoops and rods.) No change took place in miners’ wages in Durham in connection with the above ascertainment—wages remaining at 1074 P®1’ cent, above the standard, plus the war wage of Is. 6d. per day to men 16 years of age and over, and 9d. per day to boys under 16. In the North of England the ascertained prices of manufactured iron for the two months March and April resulted in an increase of wages of 3d. per ton to puddlers and 2 j per cent, to millmen. These increases are merged with the bonuses of 12| and 7J per cent, granted to time workers and piece workers respectively, in accordance with the conditions under which the bonuses were granted. No change in wages took place as a result of the ascertainments in the Midlands and the West of Scotland. Disputes.—In mining and quarrying eleven new dis- putes occurred, involving 50,513 persons. A dispute affecting underground and surface workers near Don- caster, relative to the dismissal of men who had entered