600 THE COLLIERY GUARDIAN. September 20, 1918. declares dividends at the rate of 31 per cent, during a life of nine years, and allowing interest at 10 per cent, and investing redemption fund at 3 per cent., we have— Redemption fund — —- = 0 0984338 ; and from above formula (2) the present value of the annuity is equal to— __________________1_________________ Profitable interest -f- redemption fund = o-l + 0-0984338 ’ 0’1984338 = 5 03946 Therefore the present value of an annuity of £1 for nine years is £5*03946, and on the total divi- Table J.—Summary. Block No. Planimeter reading. Dip. Area factor. Inclined i area. Stope width. Ton fa tor. Tons. Value dwts. Contents (Tons x value). Col.l. Col. 2. Col. 3. Col. 4. , ; Col. 5. Col. 6. Col. 7. Col. 8. Col. 9. CoL 10. 1 3,875 38 22 0315 85,372 48 7*34386 28,457 7-8 221,964 2 1,047 32 20'4718 21,434 48 6'82392 7,144 7'3 52,151 i 106,806 48 | 1 35,601 7 7 274,115 MINE RESCUE APPARATUS RESEARCH COMMITTEE: FIRST REPORT.* RECOMMENDATIONS REGARDING RESCUE APPARATUS. (Continued from page 550.) Care of Apparatus. Rusting of Oxygen Cylinders.—An examination was made of the cylinders of three apparatus to ascertain the degree of rusting. Patches of rust were found in them all. All apparatus fitted with a pair of cylinders have connections of narrow bore. So far as our own observations go, the Weg is the only one in which an bag is then allowed to fill up. A deep breath is then drawn from the apparatus and exhaled through the nose. The nose is now clipped. In this way nitrogen is swept out from the apparatus and the lungs. Unless the relief valve automatically discharges from time to time as the work proceeds, it is advisable before attempting any specially heavy work to empty the bag by squeezing the air through that valve, then filling up afresh with oxygen. The majority of instructors favour the provision of an oxygen by-pass. Those of the reverse opinion base their objection on the possibility of misuse. The most suitable mechanical arrangement of the by-pass will be discussed in a later report. Official Requirement as to Oxygen Purity.—The “ Memorandum on Schemes of Training and Practice,” in the Home Office pamphlet relating to rescue work,* states as follows: “ Where oxygen breathing appa- ratus is used, care must be taken to ensure a high standard of purity in the oxygen used, and supplies, unless guaranteed by the manufacturers, should be tested by analysis. The Secretary of State is advised that it is not practicable entirely to exclude the presence of nitrogen, and that, provided the nitrogenf present does not exceed 2 per cent., the safety of the users of the apparatus will not be endangered. Oxygen containing a greater amount of nitrogen than 2 per cent., or any other impurity, would become a source of danger and could not be regarded as com- Fig. 9.—Assay Plan. BLOCK I BLOCK 2 in >6 22 15-2 6 73 6 43-7 25 14-7 25 29.1 27 104 16 240 16 “iTZ •a a a a a TF" 24 16.2 V >7 321 12 3276 _ 22-C - 3*5 7 — o .5 o 5 o o. a? 'll .? ’ • 3-7 xj- 36 5 . 31-€ Xf •3 7 4«5 TO— TL7 ?72 ^7 It-2. •2-4* ft-------- 'll’ 16 17.0 I I 1 I / / I I • / I / / t J / 4- ♦/ •Y - A - m it L Si IO 11 V- 36 147 |G-I 23 G 41-4 46-5 46-4 44-7 <6 4 4A3 U7. 4 33 O I** • nJ IllA 2o- 3 15 - 43 • rx 17 - 4« 3 O ill 33.5 16 H-3 6-HLevel West. T? ’iF" 32 _29_ 125 ’7e >8 24 •e -• 14 ‘ ’ M $ I 1 24 5 U >8 ‘ 0 SzliS , II — ‘*7 7 il, ■so 17 ~ HO IB 33 C (U w • 1 a A z f 1 1 f 1 / 1 1 1 / / dend of the above company this will be equal to 5-03946 x 310,000 = £l,562,232. Therefore, there being 1,000,000 shares, the value per share is Woo = £1 lls- 3d‘ SHORTAGE OF COAL. Re-opening* of the Main Coal Seam at Coed Talon Collieries. The above took place| on Saturday, September 7, in very broken weather, but notwithstanding this there was present a very large assembly of people from the surrounding district. The opening ceremony was per- formed by his Majesty’s chief inspector of mines for the Lancashire, Cheshire and North Wales District, Mr. A. D. Nicholson, in a very few appropriate words. Speeches were made by H. S. Higginbottom, chairman of the Coed Talon Collieries, Mr. T. Parry, J.P., of Mold, whose name is well known in the district, especially in connection with coal mining, Mr. D. Darlington, manager of the Coed Talon Collieries, and Mr. Wm. Jones, of the Miners’ Federation, also spoke. Mr. Higginbottom pointed out that with the mutual assistance and co-operation of the miners, the Coed Talon area would eventually become one of the great coal-producing districts in the United Kingdom. That had only been made possible by unstinted determination and foresight, combined with the assistance of the officials in unwatering the district. Already some three million tons, or in other words, 672,000,000 gallons, of water had been drained from this district by the pumping plant at the Cae Gwen Station, and the company were now making arrangements to put down a permanent pumping plant to deal with any quantity of water which may be likely to find its way into the workings. It was confidently anticipated that before six months had elapsed the present output would be more than doubled, and no emphasis was needed to show the great national importance of this at the present time. After the opening ceremony had taken place, the first wagon of coal drawn from the pit was loaded. It was presented to Mr. T. Parry, J.P., for the benefit of the Red Cross and other local charities. Following this, sports for the colliers and their friends took place in an adjoining field, where a very extensive programme of events, with full lists of entries for each, was carried out. All the prizes, which were of a superior character, were kindly given by friends, and caused keen competi- tion amongst the entrants. The late Mr. Harris Bigg-Wither, for a generation the general manager of the Roburite and Ammonal Company’s works at Gathurst, near Wigan, left estate valued at <£6,583. To encourage the men employed at its Notts and Derby- shire collieries to burn less coal, the Bolosover Colliery Company is allowing them 16s. 6d. for every ticket which entitles the miner to a ton free. attempt is made to prevent rust entering the con- necting pipe. Graphite in Valve Glands. — The dust from the inside of a Proto reducing valve was examined under the microscope. It was found to consist mainly of particles of graphite which had entered from the valve glands. An accumulation in the reducing valve orifice of these particles, or of rust, in the manner suggested by Messrs. Rowan and Parker is not by any means out of the question, and, were it to occur when the apparatus was being worn in irrespirable air, would probably lead to the loss of a life. Cleaning of Cylinders.—A filter gauze will always be valuable as a safeguard, but the best way of coping with rust and scale is to attack it at the fountain head and prevent its formation. Every time a cylinder is annealed (unless the annealing be done in an oxygen-free atmosphere) some scale and rust is made. Immediately after annealing, the cylinders should be scoured inside to remove oxide, and then given a coat of varnish or otherwise protected against corrosion. The problem of rendering an iron or steel surface rust- proof has received a good deal of attention of late years, and it may well be that experience will even- tually point to some other mode of protection as superior to varnishing. Purity of Oxygen. Nitrogen in the Oxygen Supply.—When the wearer of a constant-rate oxygen-feed apparatus, set to supply two litres per minute, is doing work (such as building a stopping or erecting a brattice) which involves only moderate respiratory exercise, the blow-off valve is frequently in action and the apparatus is being con- tinually flushed out; but if heavier labour is per- formed, the demand for oxygen may equal or exceed the supply, in which case the relief valve ceases to discharge, and the wearer no longer has the benefit of the scavenging action of excess air. The nitrogen existing as an impurity in compressed oxygen now begins to accumulate in the circuit, and, unless the supply is in a high state of purity, the oxygen per- centage in the air passing to the lungs may rapidly diminish, although the bag remain normally distended. If this action goes far enough, the wearer will suddenly lose consciousness. To get rid of accumulated nitrogen is important in all apparatus of the regene- rator type; it is doubly important in the case of apparatus (e.g., the Weg or Gibbs) in which the oxygen feed is automatically determined by the degree of deflation of the apparatus. In the first place it is a mistake to fill an apparatus that has just been put on with air drawn in through the nose and expired into the bag. The object should be to reduce the volume of nitrogen in the apparatus at the start, and not to add to it. The wearer should therefore begin by sucking the bag flat and exhaling through the nose. The oxygen being turned on, and the mouthpiece orifice being closed by the tongue, the * See Colliery Guardian, September 6, 1918. plying with the requirements of the regulations.” The rescue stations buy their oxygen from one or other of the ten factories of the British Oxygen Company. On a label attached to each charged cylinder the company guarantees the high degree of purity of the gas, the guarantee usually being to the effect that the gas contains from 98-5 to 99*5 per cent, of oxygen. Doubtless, before the war, this extremely satisfactory proportion was realised, but, owing to the pressure of war orders, the company has recently been unable to maintain that standard in several instances. In 1917 samples of oxygen were taken on several occasions, and these were subsequently analysed by Dr. Briggs. Only six of the fourteen samples analysed conform to the Home Office requirements as to purity. Out of fourteen other samples analysed by Mr. Graham at the Doncaster Coal Owners’ Laboratory in 1917 up to August only three conformed to the standard, and one contained less than 80 per cent, of oxygen. The situation here revealed is grave. The most perfect breathing apparatus is dangerous if sup- plied with oxygen as impure as several of the results indicate. On receipt of these figures Mr. Walker wrote (September 21, 1917) to each rescue station to call attention to the necessity of analysing all oxygen supplied for rescue work in order to ascertain whether it is of the required purity, and suggesting that the analyses should be recorded in a book kept at the station. Oxygen containing more than 2 per cent, of impurity should never be used in actual work or prac- tices underground with the apparatus, nor in any situation where a member of a brigade is liable to get out of sight of the instructor, and compressed oxygen holding more than 3 per cent, of impurity should not be used for self-contained apparatus in any circum- stances. I The superintendent should endeavour to build up the emergency (two days’) stock from the purest oxygen available. This is easily done when every cylinder’s contents are analysed. With lung- controlled apparatus additional precautions should be taken against the accumulation of nitrogen, and with such apparatus the purity should be over 99 per cent. The electrolytic oxygen generated at the Birkenhead and Wolverhampton Works of the British Oxygen Company is of great purity. Freedom from hydrogen is the most important consideration with this class of oxygen. Volume for volume hydrogen is more dangerous than nitrogen, owing to the possibility of an explosive mixture being developed within the appa- ratus with the former gas. The excellence of the quoted analyses should not be accepted as proof of a * Mines and Quarries, Form No. 72, 1915, p. 3. + The impurity in oxygen prepared by the liquefaction process, though spoken of as nitrogen throughout this report, is mainly argon. In one analysis given by Morey (Journ. Am. Chem. Soc., 1912, xxxiv., p. 491), the im- purity amounted to 3-1 per cent., of which 2-8 per cent, was argon and 0-3 per cent, nitrogen. + These remarks do not apply to liquid air.