February 16, 1917. THE COLLIERY GUARDIAN. 331 with a given sparking arrangement. Pressures lower than atmospheric were obtained by lowering the mercury in the levelling bottle the required distance below that in the explosion pipette. Table 3 shows the results obtained. The second column gives the pressures. The third gives the per- centage of methane, the fourth gives the percentage of air, and the fifth gives the result as observed with the eye. Table 3.—Results or Experiments to determine Ex- plosibility of Methane-Air Mixtures at Pressures less than Atmospheric. Pressure Test No. Mm. of mercury. Methane. Air. Result. Per ct. Per ct. 1 ... ... 550 .. ... 5'59 . 94'41 . No propagation. 2 ... ... 600 ... . 5'59 . 94'41 Do. 3 ... ... 500 ... ... 5'83 . 94T7 . Propagation. 4 ... ... 450 ... ... 5'63 . ... 94'17 . No propagation. 5 .. ... 450 ... ... 6'01 . 93'96 Do. 6 ... ... 500 ... ... 6 04 . ... 93'96 Propagation. 7 ... ... 450 ... ... 6'13 . 93'87 . No propagation. 8 ... ... 500 ... 613 . 93'87 . Propagation. 9 ... ... 370 ... ... 7'03 . 92'97 . No propagation. 10 .. ... 400 ... .. 7 03 . 92'97 . Propagation. 11 .. .... 320 ... ... 7'87 . ... 92'13 . No propagation 12 ... .... 350 ... ... 7'87 . 52T3 . Propagation. 13 ... .... 300 .. ... 8'50 . 91'50 Do. 14 .. .... 250 ... ... 8'50 . 91'50 . No propagation. 15 .. .... 250 .. ... 9'00 ... 910'1 Do. IB .. .... 301 .. 9'00 . : 1 Oo . Propagation. 17 .. ... 300 ... ... 9'50 . 90'50 Do. 18 .. .... 2.0 ... .. 9'uO . ... 90'5u . No propagation. 19 .. .... 250 . ...10'00 . 90'00 . Do. 20 .. .... 300 ... ...10'00 . 90'00 . Propagation. 21 .. .... 350 ... ...10'30 89'70 . No propagation. 22 .. .... 400 ... .10'30 . 89'70 . Propagation. 23 . ... 350 ... ...10’75 . 89'25 . No propagation. 24 ... ... 400 ... 10'75 . 89'25 . Propagation. 25 ... ... 1100 ... 89'0 > . No propagation 26 ... 500 ... . 11'00 . 89'00 . Propagation. 27 ... ... 450 ... ...11'50 . .. .. 83'50 . No propagation. 28 ... ... too ... 11'50 . 88'50 . Propagation. 29 ... ... 500 ... ...12'00 . 83'10 . No propagation. 30 ... .. 550 ... ... 12'00 .. 88'00 . Propagation. It will be observed that the inflammability of the various mixtures decreased as the pressure was lowered. until it was foui nd impossible to propagate flame in any mixture at pressures between 250 and 300 mm. of mercury. In test 1 a mixture of methane and air containing 5 59 per cent methane did not propagate flame when the pressure was 500 mm. of mercury, but propagated flame when the pressure was 600 mm. In test 2 a mixture containing 5 83 per cent, of methane propagated flame when the pressure was 500 mm., but did not at 450 mm. The same procedure was followed in all of the t°sts. A certain mixture was prepared and the pressure varied to find at what pressures the mixtures did and did not propagate flame. The lowest pressui es at which propagation was recorded were SOO mm. for mixtures containing 8'5, 9, 9'5 and 10 per cent, of methane. In other words, the mixtures most sensitive to inflammation at low pressures lie between 8'5 and 10 per cent, methane under the particular conditions of experiment adopted. Effect of Varying Source of Ignition. The method of igniting the mixtures was found to have a vital influence on the results, and accounts for the somewhat irregular nature of the curve. A spark from an induction coil driven by t dry cells was the source of ignition, as in the other tests recorded herein. The platinum points across which the spark jumped were one-sixteenth inch apart. In the tests at low' pressure some of the mixtures would propagate flame by the prolonged passage of the spark when an instantane >us spark would not inflame them. Instantaneous sparking was the method adopted. Some experiments were also performed in which ignition was caused by pulling apart two No. 12 gauge copper wires through which a current of 4 amperes at a pressure of 220 volts was passing. With this form of ignition a mixture of methane and air containing 9 per cent, mi thane and under a pressure of 200 mm. propa- gated flame. No such inconsistencies were observed in explosion experiments at atmospheric pressure. The low limit of complete propagation was found to be practically the same w.th tin- spark from the induction coil as with a much larger electric flash. These results show that the energy of the spark or flash is a factor of much importance; but when the igniting arrangement is constant, or nearly so, the important factor that determines ignition is the heat of combustion of the gases. When the pressure of the gas mixture is reduced the ratio of the heat absorbed by the surroundings to the heat of combustion of the gases increases until a cooling effect is set up that is pronounced enough to prevent propagation of flame throughout the mixture. Conclusions. When the initial temperature of methane-air mixtures is 500 degs. C., the low limit of complete propagation of flame of the mixtures is between 3'75 and 4 per cent, methane. As the initial temperature decreases from 500 degs. Cent, the low limit increases unt il at ordinary temperatures it is about 5'5 per cent, methane. Differences in the initial temperature of as much as 200 degs. Cent, higher than ordinary temperature reduce the low limit from 5'50 per cent, to between 4'98 and 5'15 per cent, methane. Initial pressures as high as 5 atmospheres have no effect in changing the low limit of complete propagation of flame in methane-air mixtures. At pressures between 250 and 300 mm. of mercury mixtures of methane and air were not ignited by the igniting arrangement chosen. The mixtures that will propagate flame at the lowest pressure contain from 8 5 to 10 per cunt. methane, and therefore are more sensitive to ignition than mixtures near the upper and lower limits. The results are important in that they show that pressure temperature conditions may vary over rather a wide range without affecting the explosibility of methane-air mixtures. Inconsistent results that have been obtained in the laboratory by different investi- gators on the limits of inflammation of methane-air mixtures cannot be explained on the basis of slight variations in temperatures and pressures. They depend rather on the nature of the source of ignition, method of ignition, size and shape of the containing vessel, and in some cases inaccuracies in mixing and analysing the gases. As the low limit of complete inflammation for methane-air mixtures is not changed at pressures as great as 5 atmospheres, it can be stated that even in the deepest coal mines the low limit is not different from the limit at ordinary pressures. THE “PERFECTA” BOILER CIRCULATOR. The increased cost of fuel has sharpened interest in boiler economy to such an extent that an appliance like the “ Perfecta ” boiler circulator possesses a special interest as an economic factor in the better utilisation of boilers for industrial purposes. The great end in view, as every boiler owner realises, is a perfect circulation of the water, combined with the minimum expense in the consumption of fuel, the fuel economy being an assured sequel if the circulation is all that it should be. In this connection the manufacturers of the circulator under consideration make it clear that they are prepared to stand upon the records of actual experience collected from many sources. The circulator is a simple automatic device, and the mode of operation is easily understood by reference to the illustration. A hood or covering is made to cover the crowns of the furnaces. When steam bubbles, rising vertically under the influence of heat, burst under the circulator, they create a flow of water towards the back of the boiler, where the current takes a downward direction and returns along the bottom of the boiler to the furnaces. This motion is very rapid, and ensures perfect circulation of the whole of the water which, being brought continuously into contact with the hottest parts of the boiler, a uniform temperature is Sectional View of Circulator. produced and the steaming capacity increased. The ceaseless flow of the water set up by the circulator causes all sediment and foreign matter to settle in the right direction, where it can be expelled at suitable periods. Prom the standpoint of the most elementary engi- neering it is easy to perceive that certain advantages must accrue from the efficient production of a current in the manner described. For instance, the unequal expansion of the plates is avoided, thereby eliminating the drawbacks incidental to strains. In preventing the steam bubbles rising immediately to the surface of the water, priming is prevented, and a regular supply of steam is obtained with a greatly decreased saturation. All these results are effected without the di filing of any holes in the boiler for the purpose of installing the apparatus or interference with any existing fittings. It is stated that the apparatus has been proved to give from 12 to 15 per cent, of increased steam, or 6 to 8 per cent, saving of fuel. Apart from the direct saving thus effected, the longer life of the boiler must be taken into account as part of the estimated gain. The list of advantages claimed by the makers includes:—Improved conditions of raising steam in half the time ; supplying 12 to .15 per cent, increased steam, with minimum saturation; avoidance of priming; the prevention of scale by the rapid circulation of all matter; the freedom from pitting and grooving ; reduced trouble in cleaning, and the economy effected by the minimum of water-softening arrangements required. Practical demonstrations are carried out at the makers’ offices (39, Victoria-street, S.W.), where model boilers under steam show how the “ Perfecta ” operates automatically. War Loan Subscriptions.—Subscriptions to the War Loan include:—Wilsons and Clyde Coal Company Limited, 41142,000 ; Sir John Watson, £120,000 ; Wm. Baird and Com- pany (Glasgow), 4250,000; John Watson Limited (Glasgow), £230,000. Improvements in Labour Exchanges.—Mr. John Hodge, Minister of Labour, received at Montagu House a deputa- tion from the Parliamentary Committee of the Trade Union Congress, with respect to resolutions affecting the Labour Exchanges and other matters referred to at the Birmingham Trade Union Congress. Mr. Hodge assured the deputation that it was his intention to improve the status and administration of Labour Exchanges to fit them adequately and efficiently to deal with the after-war problem of demobilisation. It was intended to issue cards to the men, so as to facilitate their speedy return to their own employment. THE DEVELOPMENT OF INDUSTRIAL RESEARCH. The organisation and development of scientific and industrial research was the subject of a discussion at a meeting of the Manchester Association of Engineers on Saturday. Mr. Alfred Saxon, the representative of the A ssociation on the Standing Committee on Engi- neering in connection with the Board of Education’s scheme for scientific and industrial research, in the course of a paper drew attention to a report issued by the committee of the Privy Council, in which it was stated that “ many of our industries have since the outbreak of war suffered through our inability to produce at home certain articles and inaterials required in trade processes, the manufacture of which has become localised abroad, and particularly in Germany, because science has there been more thoroughly and effectively applied to the solution of scientific problems bearing on trade and industry and to the elaboration of economical and improved processes of manufacture. It is im- possible to contemplate without considerable appre- hension the situation which will arise at the end of the war unless our scientific resources have previously been enlarged and organised to meet it. It appears incontrovertible that if we are to advance or even maintain our industrial position we must as a nation aim at such a development of scientific and industrial research as will place us in a position to expand and strengthen our industries and to compete successfully with the most highly organised of our rivals. The difficulties of advancing on these lines during the war are obvious and are notunder estimated, but we cannot hope to improvise an effective system at the moment when hostilities cease, and unless during the present period we are able to make a substantial advance we shall certainly be unable to do what is necessary in the equally difficult period of re- construction which will follow the war.” At first the scheme was framed to cover the United Kingdom, but it had now been decided that it should operate throughout the whole Empire, and that there should be complete liberty to utilise the most effective institutions and investigators available, irrespective of their location. The scheme accordingly provided for the establishment of a committee of the Privy Council responsible for the expenditure of any new moneys provided by Parliament for research purposes, and a small advisory council responsible to the committee of Council, composed mainly of eminent scientific men and those engaged in industries dependent upon scientific research. Three standing committees had been appointed by the Advisory Council to advise on researches relating to engineering, mining and metallurgy, and a circular had been issued by the Engineering Committee expressing the view that in order to obtain as comprehen- sive information as possible relating to these researches, and to avoid overlapping, it was essen- tial to encourage the co-ordination of existing researches, and plan, to the best advantage, schemes for the creation of new researches. In his (Mr. Saxon’s) opinion, firms would be wise if they made the outlay on research a standing charge in the same way as rent was, and he was sure it would pay. It might even be necessary, in order to take a successful part in the industrial war which would follow the struggle on the Continent, to extend the Government control now existing, into the industrial warfare. Business men had been introduced into the councils of the country, and it seemed likely that in future there would be more business and less politics than in the past. Firms, however, would have to sink a great deal of their individuality and be pre- pared for State control, particularly in the direction of research work, unemployment, and the upkeep of idle machinery.' Prof. Petavel (Manchester University) recommended a closer alliance between industrial concerns and the universities, and Mr. Wendeler emphasised the fact that if research was to be carried out successfully the inventor must be protected. Under existing conditions the inventor in this country was a poor miserable creature, who had to skulk into the corner while the octopi got the benefit of his genius. In the past England had been the home of the inventors, and many inventions could be produced in any works of an average size if the men knew that their names would be recognised in connection with their efforts. Sulphate of Ammonia Price Fixed.—The Food Controller, with the concurrence of the Agricultural Departments of Great Britain and Ireland, has approved of an arrange- ment whereby sulphate of ammonia is to be sold at the price of £16 per ton, 241 per cent, basis, in makers’ bags, net cash, delivered at the consumer’s station in any part of the United Kingdom. The price to consumers who take delivery at the producer’s works for conveyance otherwise than by railway remains at £15 10s. per ton. In the event of purchasers experiencing difficulty in obtaining supplies locally, they should apply to the secretary, Sulphate of Ammonia Advisory Committee, 84, Horseferry-road, London, S.W. The Food Controller has appointed the following committee of manufacturers of sulphate of ammonia to advise him with regard to questions affecting its production and distribution:—Mr. D. Milne Watson (chairman), Gas Light and Coke Company; Mr. William Fraser, Pumpherston Oil Company Limited ; Mr. E. J. George, Consett Iron Company Limited ; Mr. W. R. Hann, Powell-Duffryn Steam Coal Company Limited; Mr. N. N. Holden, Messrs. Hardman and Holden Limited ; Mr. A. K. McCosh, Messrs. Wm. Baird and Company Limited; Aider- man F. S. Phillips, Salford Corporation Gas Department ; Mr. A. Stanley, Messrs. Simon-Carves Limited; Mr. F. C. O. Speyer, secretary.