February 4, 1916. THE COLLIERY GUARDIAN. 231 payment of wages due to Churm, not from themselves, but from the collier? On the facts, they were not shown to have ever paid to anyone the full amount to which Churm wa.s entitled under the Act, and accordingly by-law 13 had never come into operation and did not avail them. The colliery company had prepared their own by-laws, and incorporated them by reference into the contract which was signed. By one by-law they promised wages; by another tney tried to stipulate that in certain cases they were to be deemed to have promised none, but they did this in a halting fashion, which, if it did not bear the above inter- pretation, bore no clear interpretation at all. He thought, therefore, that the .appeal succeeded. BOOK NOTICES. The Electrical Engineer’s Diary, 1916. Edited by V. H. Johnson, p. 318 4- diary interleaved. 10-J.in. x 8J in. London: S. Davis and Company, 30 and 31, St.' Swithin’s-lane, E.C. Price 3s. 6d. .This diary has been compiled for the use of consulting engineer's, architects, electrical contractors, central station engineers, and all users of electrical apparatus. The contents include a mass of general information and special sections on the generation of electricity, the application of electricity for power purposes, lighting, cooking and heating, also the Home Office Regulations for Mines, Factories, and Workshops. Model wiring specification, standardisation rules for eleccirical machinery, and the wiring rules of the Institution of Electrical Engineers. There is also a list of electricity supply authorities in the United Kingdom. The first 24 pages of the diary comain a dictionary of technical terms and definitions provisionally approved by the British Electro-Technical Committee, and occasionally amplified by the editors. The tabular and other technical details are well arranged and carefully selected. Much of the information has been specially compiled for the diary. We notice particularly a coal specification for electrical engineers. It is only in the case of large supply stations that coal contractors would probably supply coal guaranteed to meet a definite specification, but it is always open to an engineer to select particular kinds of coal in accordance with fuel tests, and the standard specification here given will be useful as a guide to quality in respect of calorific value, moisture, etc. The application of electricity to mining is treated concisely, and an interesting table is given showing the performances and details of electric wind- ing installations, the maximum output mentioned being six tons of coal per wind, or 2,000 tons in eight hours from a depth of 2,000 ft. There is also useful informa- tion on coal cutting, pumping, ventilation, etc. Amongst other cognate subjects ,the section on electric lighting is well treated; but it is impossible to refer adequately to the wealth of information supplied in this volume, which is so reasonable in price that electrical engineers can safely order their copy forthwith. The “ Mechanical World ” Electrical Pocket Book for 1916. 240 pp. 6 in. x 4 in. 130 figs. Emmott and Company Limited, 65, King-street, Manchester. Price, 6d. net. This pocket book contains a useful collection of electrical engineering notes, rules, tables, and data. New features are introduced, among which we may mention the valuable section on switchgears and switch- boards, with much practical information in a concise form, and several new illustrations. We notice here a special reference to mining switchgear and switchboards for underground use. Another new feature is a section on earthing, including a whole lot of useful hims upon this important subject. Other additions include par- ticulars of alkali accumulators, the Edison cell, reductors for half-watt lighting, efficiency of direct-current dynamos and switching. The o.her sections have been carefully revised and brought up to date. This 'little book is a most remarkable sixpenny worth, furnishing not only a pocket encyclopaedia, but also a set of mathematical tables and diary for 1916. A special section of this book, pp. 214-222, deals with electricity in coal mines, with sections on signalling circuits, telephones, haulage, electric winding, coal cutters, pumping, ventilation, and other subjects incidental to underground installations. The “ Mechanical World ” Pocket Diary and Year Book for 1916. 330 pp. 6 in. x 3| in. 87 figs. Emmott and Company, 65, King-street, Manchester. Price, 6d. net. This book maintains the high standard reached by this well-known series of annuals. Many new features have been introduced. Information on mechanical means of transmitting power, including descriptions of all kinds of steam engines and boilers, gas and oil engines, will be found in it in a concise form; and there are many pages of tables and other matter suitable to the require- ments of the engineer. The articles are all of an eminently practical nature. Special mention may be made here of the article on Diesel engines, and also that on suction gas producers, in connection with which are some statistical data respecting fuel. The article on steam turbines contains illustrated descriptions of all the prominent types. It is not possible to give any adequate notion of the wealth of information afforded by this little volume. The Practical Electrician’s Pocket Book for 1916. Edited by H. T. Crewe. 477 pp. 5 in. x 3-J in.; with many illustrations. S. Rentell and Company Limited, 36, Maiden-lane, Strand, London. Price, Is. net, cloth; also Rexine, with T50 insurance, Is. 6d. net; postage 3d. The editor of this well-known annual tells us that he has been able to include several new^ chapters, dealing with such subjects as electric vehicles, drills, blowers, lifting magnets, pumping plant, mining telephones, shaft signals, and other up-to-date matters, to which is added, at, the higher price indicated above, an insurance policy in the event of death from electric shock. This pocket book has now completed its 17th issue. Of the sections more particularly applying to collieries, we may draw attention to the sections on coal-cutting machinery, elec- tricity in coal mines, and colliery switchgear. Electricity in coal mines occupies 18 pages, but so large a part of the matter contained in this volume is of general application, that the colliery electrical engineer will find little or nothing which is wholly foreign to his requirements. There seems to be a tendency in the present day to change somewhat the style of these pocket books, replacing mere tabular information by specially written articles on technical points. The editor has been fortunate in securing for this purpose a number of highly-qualified contributors, whose work has added considerably to the value of the book. As before, there is a section dealing with central electric lighting stations of the United Kingdom, which has been specially pre- pared for the use of manufacturers of plant and apparatus, installation contractors, and users of current. We can certainly endorse the claim that, as a technical work of proved accuracy and practical utility, this pocket book is well wrnrth its moderate price) Business Prospects Year Book, 1916. Edited by Joseph Davies and C. P. Hailey. 216 pp. 7 in. x 4f in. Cardiff : The Business Statistics Company Limited.' London : The Financial Times, 12, Coleman-strect, E.C. Price, 10s. net. This is the tenth year of issue of this important business year book. The editors have given due con- sideration to the weighty question of the dura.ion of the war, which must be a ’ factor of some uncertainty in any forecast of business for the present year. Signific- ance is attached to the fact that business men abroad are already devoting their attention to after-war prospects, and we cordially approve of the opinion expressed in the preface to this volume that business men in this country should be prepared for any eventuality that may arise; It is the general opinion of the editors that the immediate resul.s of peace will be to bring about a great demand for the replenishment of stocks allowed, to run short during war conditions. They also maintain that the amazing rapidity with which our manufacturers have accommodated themselves to the making of munitions is an index of the speed with which reversion to peace routine will be possible. The process of recovery abroad will probably be less rapid. Is it quite correct to say that the markets untouched immediately by this stupendous conflict will have no after-war problems to solve? We believe that places like South America, China, and other areas will be considerably embarrassed after the war by German efforts to re-establish a commercial footing in those districts, especially as things seem to point to forced restrictions in their sphere of operations in countries allied to ourselves. We unhesitatingly recommend this useful book to the careful attention of business men engaged in industries connected with coal and metal mining, oil, shipping, wheat, cotton, rubber, and even the money market, which rules everything. The book is full of statistical and other information not otherwise easily to hand when wanted. It is a book sui generis, and also indispensable. LECTURE ON “ COAL.” The third of a series of lectures on “ Coal,” by Dr. Marie- Stopes, was delivered on Tuesday, February 1, 1916, at University College. The lecturer said that bogheads have generally been interpreted as being not only different in their external qualities, but having a fundamentally different origin from ordinary bituminous coal. Largely owing to -5'6- 2X- Track I ^"Cable7’ -----3'1^ the work of two distinguished French palaeontologists, Renault and Bertrand, the view became widespread that these coals were preponderatingly formed by algae. The name Pila bibractensis was given to these supposed algae, which were described as being microscopic aggregates of cells. Similar organisms were discovered in kerosene shales, and owing to the wide acceptance of this interpretation of the structures by geologists, it has been almost universally accepted that these peculiar gelatinous algae were the forming organism of bogheads and oil shales. The lecturer pointed out the difficulties and inconsistencies into which this view has led its followers, and agreed with the view propounded by Jeffrey, and recently fully substantiated by Thiessen, that these structures bear no relation whatever to algae, but owe their fictitious appearance of cellular struc- ture to the wrinkling and slight decomposition of the exines of the spores of which they are really formed. The lecturer showed illustrations and thin sections of the supposed algae, which demonstrated clearly that they were spores, the con- clusion being that the “ algal theory ” has no foundation in fact, either for bogheads or oil shales. The persistence of spores and their extraordinary powers of resistance to decay were illustrated by experiments with coal which had been treated by the most active chemical reagents. Hydro- fluoric .acid, followed by nitric acid and potassium chlorate, will almost completely dissolve the whole substance of coal, but, in the fine granular debris which is left, spores abound and are uninjured. In connection with the idea of a gelatinous mass suggested by the algal hypothesis, the lecturer dwelt on the importance of a jelly-like magma in the formation of some coals. Whilst not agreeing entirely with all Prof. Potonie’s deductions, the importance of his discovery of “ sapropel,” a jelly-like substance formed by plankton on the lake bottoms of undisturbed waters, was recognised. Samples of “sapropel” were shown, and its method of origin illustrated. It was compared with some remarkably interesting flints from Asia Minor. These, though composed of silica like ordinary flints, are permeated by sapropel fragments in which the pollen grains of Finns are conspicuous, just as they are in recent sapropel. These remarkable flints are, in fact, a fossil sapropel which has been permeated by silica, instead of forming a coal bed as, in other circumstances, the mass might have done. In this case, also, the unique indestructibility of the spores was illustrated; hydrofluoric acid, which completely dissolves the whole substance of the flint, left the little pollen grains unaffected. Before generalising on the composition of coal, further data will be given, but the lecturer here pointed out the supreme importance of spores as a source of resins and waxes in coals and oil shales of all kinds. (The next lecture will be on Tuesday next, February 8, at 5 o’clock, and is open free and without tickets to all interested in mining, etc.) Erratum.—In the report of last week’s lecture, on p. 166, too blackened and altered for recognition microscopically,” should read “ too blackened and peered . . . macroscopically.” MINE VENTILATING DOOR.* At the Gardner and Spray shafts (Copper Queen Mine) the mine fan draws the air down and forces the whole into the workings on the 900 level. Fart of this air goes down to the 1,000 ft., and later comes up to the 900 ft., from whence all the air passes through stopes to the 800 ft., 700ft.‘and 600 ft. levels, and exhausts through abandoned workings and upcast shafts. On the 1,000 ft. level the pressure is built up by the use of automatic doors, which not only hold the pressure, but also allow the air to circulate freely on the level. The usual speed of motor trains passing through these doors is about 7 miles an hour. The doors are 350 ft. apart. The arrangement for automatically open- ing the door is shown in the illustration. When the motor comes in the direction of C to D, the motorman reaches out and moves the lever C in the direction the motor is going. This opens the three-way valve B, admits compressed air into the cylinder A and opens the door. When the train has passed through the door, the motorman throws the lever D, which releases the compressed air, and the door closes, assisted by the weights E and F. The valve G controls the speed of opening and closing of the door. ■ The wires between C and D are crossed, so that the levers are always moved in the direction the motor is going in opening and closing the door. The distance between the lever C and the door is 70 ft., which allows ample time for the door to open when the motor is coming at an ordinary rate. The distance between D and the door is 175 ft. This makes it possible for a trip of cars to be in front of the motor on the return, and at the same time allow the door to be opened. The cost of upkeep is small, and the entire equipment only requires the amount of attention usually given to any machine. The automatic doors are used on motor tracks only, while small hand doors are used in all ordinary drifts. The standard hand door is 6 ft. 6 in. high, 3 ft. 9 in. wide, and ,2| in. thick, made up of lin. boards with paper between the two thicknesses. The posts of the door frame are 6 in. by 10 in. by 6 ft. 6 in., and the cap 6 in. by 10 in. by 4 ft. 3 in. The motor tracks are mounted on a timber sill set in concrete. The space between the bottom of the door and the sill is filled with concrete, except for clearance spaces for the flanges of the car wheels. The spaces between the door frame and the walls and roof are. likewise filled with concrete. The automatic door is 6 ft. 11 in. high by 4ft. 4in. wtide, made of lin. by 12in. boards, faced on both sides with | in. by 2 in. flooring. * Mining and Engineering World.