March 1, 1918. THE COLLIERY GUARDIAN. 433 new retorts would require to be built, so that it seems preferable to build retorts for low-temperature car- bonisation in districts in which rich cannel exists. The shale oil process is intermediate between high and low temperature, and does not give as large a yield of oil as low-temperature plants, owing to the fact that the retorts are worked for ammonia recovery; in fact, the recovery of ammonia was the salvation of the shale oil industry. From considerable experience, the author would put the average quantity of fuel oil obtainable by the car- bonisation of one ton of cannel at 20 gals. That is to say, if 15,000 tons of cannel per diem were carbonised, some 300,000 gals, of oil would be produced, or 105,000,000 gals., working the plant for 350 days in the year ; and there is also to be taken into account the amount of light oil and paraffin wax produced. The amount of creosote oil produced from one ton of tar varies considerably, but if we take it that, on the average 40 gals, is produced, and that 12 gals, of tar is obtained by the carbonisation of coal in the gas ..... Fig. 1.—Whitworth Measuring Machine. retorts of the United Kingdom, it will require about 16 tons of coal to produce one ton of tar, that is to say, to produce 40 gals, of creosote oil. On the other hand, by carbonising 16 tons of cannel, which, as stated above, may be expected to yield 20 gals, of fuel oil per ton, 320 gals, of fuel oil will be obtained. Further- more, except to a limited extent, cannel coal is not suitable for gas works practice or for domestic use. MECHANICAL COAL BARCE TOWINC TEST. On Tuesday, February 26, a long distance towing test was made by the Watercraft Detachable Power Installations Limited, of Central House, New-street, Birmingham, with one of their type “ A ” portable motors for canal barges (described in Colliery Guardian, May 11, 1917, p. 898). The towing test was made in conjunction with Messrs. Guest, Keen and Nettlefold Limited, of Smethwick, one of whose coal barges was fitted with the motor and served to tow a second barge. The outward journey (light) was commenced at 12.15 on Tuesday morning, from the works at Smethwick, along the Stour Valley Canal to the Factory Locks at Tipton (three in number). After negotiating these three locks, the two barges were on the level for the remainder of the journey. Mr. T. H. Coggins, of Coggins and Arthur, the pioneer of this type of mechanical haulage, who is also the chairman of the Watercraft Co., accompanied by Mr. A. E. Hooke, the managing director and inventor of the system, were in charge. The route followed from Tipton was via the Cosely Tunnel, Deep- fields, Wolverhampton, Wednesfield, Short Heath, Blox- wich, BirchiUs. the Wyrley and Essington Canal, and the Hednesford Arm, and the two empty barges arrived at the Mid Cannock Colliery Basin at 7 o’clock in the morning, having accomplished the total distance of 28J miles in 6 hours, 45 minutes. As a two-hour wait at the colliery was essential for loading the boat with the motor attached, the return was not started until 9.15 a.m. The towing capacity of the engine left nothing to be desired, and the two loaded barges arrived at Messrs. Guest, Keen and Nettlefold’s works at 7.15 p.m., the return run having taken 10 hours. When the tortuous configuration of the Birmingham canal system is taken into account, and the number of “bridge holes” which have to be negotiated at slow speed, it will be apparent that the performance was in the highest degree satisfactory The canal is full of traffic going both ways, and much of the progress is necessarily slow where there is any congestion of boats. The proof of the great superiority of the motor-driven barge lies in the fact that, although towing the second loaded barge, no difficulty was experienced in overtaking and passing numerous single horse-drawn barges, and that, for the horse-drawn single barge, this particular journey usually takes two days for the outward and home trip, whereas the motor took two barges empty and brought back two fully loaded ones in 19 hours, including a stoppage of two and a-quarter hours at the colliery. Institution of Civil Engineers___A paper on “Modern Developments in Gas Works Construction and Practice,” by Mr. A. Meade, will be submitted for discussion at a meeting of the Institution of Civil Engineers, Great George- street, Westminster, on March 5, commencing at 5.30 p.m. British Miners Gift to Dutch Miners. — The Miners’ Federation of Great Britain, with the consent of the Treasury, has forwarded the sum of £500 to the Dutch Miners’ Association as a gift to the Dutch miners towards the support of the families of Belgian miners working in the Dutch coal mines who were re-interned for their parti- cipation in the recent strike of the Dutch miners for "a fixed minimum wage. SIR W. G. ARMSTRONG, WHITWORTH AND COMPANY LIMITED. TOOLS ANO TOOL STEEL. We recently had an opportunity of visiting the tool steel works at Openshaw, Manchester, of Messrs. Sir W. G. Armstrong, Whitworth and Company Limited, and inspecting the various stages of manufacture of their now famous high-speed tool steel for use in turn- ing, planing, and slotting machines, as well as their well-known specialties in taps, dies, chasers, and gauges. The late Sir Joseph Whitworth will ever be remem- bered as the inventor of the standard screws, but it may not be so equally well known that he was also the inventor of the “ surface ” plate, and the first machine for accurate measurement. With regard to the former, we were shown the first “ surface ” plates ever- made, which have so true a surface that when one is superimposed on another, with a sliding movement so as to exclude the air, the upper plate will support the weight of the lower one, through the effect of the atmo- spheric pressure acting on the exterior of the plates. The Whitworth cylindrical gauges were appointed (by an Order in Council dated August 26, 1881) legal standards in this country, and are deposited in the Standards Department of the Board of Trade. Fig. 2.—Screw Gauges for Bolts, Nuts, &c. The invention of the measuring machine made these standards possible, and no other method has yet been put forward for measuring to within such fine limits. In this machine the sense of touch is relied upon, instead of that of sight, and the original machine, capable of measuring to the one-millionth part of an inch, is still preserved at the Openshaw Works. Naturally, one has to become expert in the sense of Fig. 3.—Whitworth Standard Internal and External Cylindrical Gauges. touch when dealing with such very minute dimensions, but the difference in the sense of touch between zero and one one-thousandth part of an inch is very appre- ciable indeed. Several of these machines, in charge of expert measurers, are in constant use in the gauge department. The machine is shown in fig. 1, and at first sight looks like a small lathe. The bedplate and head- stocks are accurately machined. The right-hand head- stock is fixed, and contains the measuring screw, which is operated by the large wheel, the edge of which is divided, each division representing 0'0001 in. end movement of the screw spindle. The bedplate is also' divided to enable the movable headstock to be set quickly into the best position without having to try the standard; whilst the small hand wheel is divided to enable fine adjustments to be made, especially when the headstock has been set up too tight, and requires easing back. In moving both these hand wheels, it is necessary to set them back much further than required, and then bring them forward to the proper dimension, so as to avoid black lash error in the screws. At the top of the large hand wheel is a vernier, which, as used at Openshaw, measures to 0-00005 of an inch, this being the limit of error of the firm’s gauges. Assuming that a new gauge, say, 0-0342 in. longer than the 6 in. standard gauge, is to be made. First, the standard gauge is put in, as shown in fig. 1, rest- ing upon the two supports, with a gravity piece between the end of the gauge and the contact on the right hand spindle. The measuring wheel is set at zero, and the small hand wheel adjusted until the gravity piece just drops out by its own weight. The standard is now removed, and the longer gauge put in. One complete revolution backwards (equal to 0-05 in.) is given to the hand wheel, which is then moved for- ward again to 0'0342 in. If the gauge is the right length, the gravity piece will now drop out by its own weight—-if too tight or too slack, the difference, either way, will be shown on this wheel. Fig. 2 shows a set of screw gauges, whilst fig. 3 shows a set of cylindrical gauges. These are made from l/16in. up to 6 in. diameter. Those up to 2 in. diameter are of hardened steel, but those over 2 in. diameter are also made in cast iron. The Whitworth standard thread dates from 1841. The angle of the thread is 55 degs., and H = 0-9605 P, where P = the “ pitch” of the thread, and D = 0-6403 P. For threads below V^in., the British Association screw thread, which is now universally used, differs from the Whitworth, inasmuch as the angle is 47-5 degs. instead of 55 degs. R = 2/11 P, and D = 0-6 P. These are used for standard gauge diameters from 0 to 16. Naturally, the manufacture of “ screwing ” appar- atus receives considerable attention at the Openshaw Works, and the taps, dies, and chasing tools are all made in such a way that absolute accuracy is ensured. A new form of stock is shown in figs. 4 and 5, termed the “ Guide ” screw stock. The dies of this stock are cut by a master tap, which is twice the depth of the thread larger in diameter than the working tap, thus making the circle of the dies in contact of the same diameter as the bolt to be cut. The inner edges of the moving dies are made to an acute angle, which enables them to cut the thread with extreme ease, and without distorting it. The directions in which they move preserve their cutting power undiminished to the full depth of the thread, the action, in fact, being the same as a chasing tool, which they resemble in form; and they may be re-sharpened upon a grind- stone. Another interesting stock is one designed for screw- ing pipes. This consists of a die box, which carries five dies, or chasers, made to be simultaneously advanced or withdrawn by rotating a scroll. A set of five guide dies on the underside of the die box moves in a similar manner to centre the die box on the pipe. The dies are interchangeable, made in sets of five, and can be ground like chasers. These stocks are made in three sizes, for screwing pipes from 1 in. to 2f in., 2 in. to 4|in., and from 4 in. to 6 in. All taps and dies are of the special steel made at the Openshaw Works, which has gained such a reputation during recent years, especially the grade known as high-speed steel.