March 22, 1918. THE COLLIERY GUARDIAN 589 cutter, which has reached a pitch of high perfection and is, to the best of our knowledge, the only survivor of this type of machine. The makers claim for it that it is more flexible 'and better adapted to average conditions than any other type. This seems to be borne out to some extent by the rapidly increasing use of these design than is the case with the majority of chain machines on the market. Although originally confining themselves to the bar construction, Mavor and Coulson deem that the manu- facturer who can offer the best bar, chain or disc cutter is the likeliest to hold the market. The “ Universal,” as cylindrical valve of very simple construction is used. By turning a milled nut the cut-off can be varied while the engine is running, to give any desired length of stroke. In the electrically-driven shaker conveyor the driving gear is usually placed in a gate, and the trough operated by means of a rope and bell crank lever; but a design Fig. 4. Fig. 7. nr =nr a machines on the Continent and elsewhere abroad, which had resulted in 1913 in the firm’s output constituting probably a record in coal-cutter manufacture. The Pickquick machine has recently undergone an almost complete transformation, from which it has emerged as the Pickwick “ Universal ” Coal-Cutter. The name seems apt as the machine is both a header, a long- wall machine, is interchangeable from electric to com- pressed air drive and from bar to chain and vice versa. Fig. 5. ■■ ■ ; sil . I’HJ HL* ><«!• // 1 '&"■ , / , ,-;Er Fig. 6 shows the new Universal machine, medium (B) size, with a bar cutting member and a d.c. motor. The total length is under 8 ft. For driving headings a 6 ft. undercutting bar is generally used, and for flitting the machine rapidly from place to place an auxiliary haulage is provided, giving a travelling speed of 50 ft. per minute. With these machines six to eight places, up to a bar- and a chain machine, has been well proved and the makers are satisfied that it has reached a stage very near perfection. The “ Samson ” disc machine was brought out some years ago with a view to meeting the demand for a Samson among coalcutters, and in this the makers cer- tainly succeeded. They perhaps overstepped the mark to some extent, since none but the most refractory sub- jects should require the colossal strength of the “Samson Senior.” Fig. 7 shows a medium size disc machine, containing many novel and excellent features, which is now being placed on the market by the firm. In this design the disc is dead in the centre—a feature Fig. 6. which seems to have been disregarded in many modern machines. A 30 B.H.P. motor is used, the over-all height is 14 in. and the length just over 8 ft. Any range of disc speed can be given, so the machine is suited to the hardest cutting or to free coal. A special feature is the complete boxing-in of all working parts and the ease with which access to these is obtained. The machine can be fitted with direct or alternating current motor or with compressed air engine. The “ Midget” bar machine is doubtless the smallest longwall is in hand for driving direct, when desired, in thin seams. Professor Kendall on Coal-seam Splits.—Professor P. F. Kendall, of Leeds University, in the course of a lecture to the members of the Leeds Philosophical and Literary Society on Tuesday, regarding “ The Rivers of the Coal Age,” confined his attention mainly to a consideration of how splits in coal seams arose. For sixty years the theory had been accepted that the break in the seam meant that the coal deposit had been washed away, and that it would, therefore, be found somewhere else. Alternatively, it was suggested that it was really to be found in the thickness of the seams on either side. The latter was an ingenious theory, but unsubstantial, and he could imagine a colliery accountant remarking, “ Well, that coal has never passed through our books.” He had spent many sleepless nights over the problem, and had come to the conclusion that the split was caused by the extreme compressibility of coal in the making as compared with the alluvial deposits. I 3 t] Fig. 8. -s— 15 ft. wide each, are being cut in an eight hours’ shift, and a 12 ft. airway was recently driven to a length of 160 ft. in eight days, averaging 20 ft. per day. The same machine is equally adaptable for longwall work without alteration, except that the undercut is usually reduced. The same machine is supplied fitted with a chain instead of a bar gearhead. The chain cuts itself in under its own power, and it is claimed that the working parts are throughout stronger and of less complicated coal-cutter of any practical value in existence. A large number of these little machines were supplied to, and on order for, Belgium prior to the outbreak of war—the very thin inclined seams in that country calling for a very special machine. Fig. 8 shows a Mavor and Coulson compressed air- driven shaker conveyor. The engine is of substantial design, with crossheads running on guides, which prevent the excessive wear of brasses which occurs in the overhung crosshead type engine. An oscillating The peat was squeezed into one-twentieth of its original space when it became coal, but the sands and shales were not compressible to anything like the same extent, so that when a river had cleaned a “ wash-out ” in the peat and left its own deposits before swinging off to another course, and perhaps leaving the peat formation to be resumed, the squeezing process, acting easily upon the peat on either side of the “ wash-out,” but met with resistance by the sands and shales, depressed the former, and left the latter raised. Hence the splits, so many of which were to be found in the Yorkshire coal fields.