988 THE COLLIERY GUARDIAN May 25, 1917. pumping acid waters. As regards couplings, although in the early days flexible couplings were used, the coupling most used at present was almost equivalent to a solid coupling, except that the connecting bolts had hard rubber sleeves, which absorbed vibration. As to dynamic balancing, he used to hold the view that this was absolutely necessary, and a dynamic balancing machine was obtained, but it was found unequal to dealing with the larger tasks, and so its application was rather limited in the first instance; but it was something outside dynamic balancing that used to bother him. The question was what was to be done if, having carried out the dynamic balancing, the Fig. 1.—Depthometer and Indicator. ,/mt. y 0 I o o o a I a I Q O ” W a/7 discharge from the periphery of the wheels was more in one place than another; and he doubted whether the expense of dynamic balancing was worth while when this other condition had to be taken into account. Consequently, although the dynamic balancing machine was kept for some time, in the end it was felt to be hardly worth while to continue it, and he believed that the practice generally was not to balance dynamically, but simply to balance individually or collectively, and not to do anything further. The President, speaking with regard to the sugges- tion as to research, reminded the members that a sum of £500 had been placed at the disposal of the council by one of the members of council, Mr. Williamson, for the purposes of research, and suggestions were now being invited with a view to making use of the gift. Any suggestion, therefore, with regard to turbine pumps would be very carefully considered. Imports of English Coal to Italy. —Jj’Union Franco- Italiano, a weekly journal published at Nice, states that the imports of English coal to Italy last year showed a decrease of 3,937,152 tons, or nearly half the total as com- pared with those of 1913. The quantity of coal exported from England to Italy during the last four years was respectively : 1913, 9,647,160 tons; 1914, 8,625,000 tons; 1915, 5,738,460 tons; 1916, 5,710,008 tons. French Licensing Regulations.—Instructions regarding the import of coal into France have been issued by M. Violette, the French Food Controller, to the Director of the National Coal Office. Licence to import coal may be granted to the importer who owns a vessel provided the coa] is intended for officially recognised purposes. If the importer is not the owner of a vessel, the licence can only be granted to a professional importer who is duly regis- tered as a coal merchant, properly equipped with the means of unloading, storage, and transport. Combinations of importers are to be formed in various groups of ports to take charge of the unloading and forwarding of the coal. Coal destined primarily for public purposes will be devoted solely to these purposes, while private requirements, such as those of the combined professional importers authorised by the Government or by groups of districts, will be decided on by the Prefect or Sub-Prefect in consultation with Chambers of Commerce or the Departmental Coal Office. Prices will be fixed only when the coal cargoes are en route. Freight contracts may be revoked even though the vessels are already laden. A third and final circular on the subject will be issued. More Miners for the Army.— The Board of Trade announces that the Government have decided it is neces- sary to release more men from coal mines for service with the Colours. After consultation with the Miners’ Federa- tion, it is proposed, in the first place, to recruit from amongst the men employed at the, coal mines those who are of military age and who entered the coal mining industry since August 4, 1914, and were of military age at that date, except only men at present engaged as (a) wind- ing enginemen, (&) pumpmen, (c) electricians, (d) fitters and mechanics, including blacksmiths, joiners, and wagon and tub makers and repairers. Accordingly, certificates of exemption of men thus becoming available for service with the Colours have been withdrawn by Order dated May 12, 1917, and made by the Home Secretary. It is, however, only proposed at present to recruit men who may be medically classified “A.” “ B ” and “C” men will be alloyed to remain in the industry. Every man becoming available for service will have the right of appeal to a colliery recruiting court upon grounds of misdescription of occupation, age, or date of entry into the industry, and to the ordinary tribunal on private grounds with the usual time limits. THE DEPTHOMETER. By-product and other works have sprung into being all over the country, due largely to the exigencies of the war, and the efficient equipment of the plants is the subject of much thought. An important need in’ connection with such plants is an apparatus for indi- cating or recording the depths of liquids in distant tanks, which, in many cases, are necessarily in posi- tions which are not readily accessible, and difficulty is experienced in ascertaining the depth of the contents, or in regulating the flow of liquid. In many instances the tanks are situated at a height Fig. 2.—Details of Depthometer. "t \ i of 50 to 60 ft. above the ground, which position adds an element of danger to the operation of the plant, and during inclement weather the requisite attention is either omitted altogether or greatly neglected. Some provision for enabling the operator to determine the contents is therefore a necessity, but an apparatus to perform this important function should possess the quality of absolute reliability, or the cure would be worse than the disease. The installation must also be perfectly safe when used on tanks containing gaseous and inflammable liquids, such as benzol, toluol, etc. Moreover, the instrument should indicate the depth, in a continuous curve from “empty” to “ full,” and must combine simplicity with the need for -the mini- mum of attention. A system having these desirable advantages to a marked degree is being put on the market by the Foster Engineering Company Limited, Wimbledon, London, S.W. The appliance is an electrical device, and is operated by a low voltage alternating current, the supply being taken from the power mains, and suitably transformed. In cases where alternating current is not available, a small motor alternator can be utilised. , The principles applied in the operation of the system, and the adoption of an alternating current, make it practicable to dispense with moving contacts, so that sparking and oxidation are entirely absent. Since no batteries are used, a prolific source of worry, unreliability, and inaccuracy is thereby eliminated. On most alternating current systems there is a cer- tain amount of fluctuation in the pressure of supply, which, if not provided for, would be fatal to the accuracy of the readings of the “depthometer” instrument. The necessary correction is adequately dealt with in the apparatus in question, so that an absolutely reliable reading is obtained. Fig. 1 illustrates the disposition of the various parts in a typical installation, and it will be noticed that only two wires are necessary to connect the deptho- meter on the tank to the indicating instrument. A number of depthometers can be connected to one instrument, by means of a plug board, where a con- tinuous reading is not required. In many instances it will be found conducive to effi- ciency of working to provide each depthometer with its own instrument, the increased initial cost in such cases being more than outweighed by the advantages derived. The claim regarding safety and immunity from danger can be appreciated from an inspection of fig. 1. It will be noticed that the whole of the current-carry- ing parts are hermetically sealed from contact with tank vapours. For the measurement of acids and other corrosive liquids, the depthometer can be constructed of acid- resisting materials without impairing the trustworthi- ness of the apparatus. Acid tanks are frequently adapted for use with compressed air to convey the contents to other levels, and it will be observed that the design of the depthometer enables the device to be used on tanks under pressure. An extremely important point in connection with the system is the facility for transmitting the readings to any distance. One installation in use is operating over a length of three miles of line. It is equally practicable to employ the instruments in connection with deep tanks or service reservoirs as it is to use the appliance in shallow receptacles. For this pur- pose the lower portion of the instrument situated in the tank or reservoir embodies a simple worm gearing in lieu of the lever motion shown in fig. 2, and the gear is operated by a float and chain, the latter mesh- ing into a sprocket wheel of a size proportional to the depth of liquid to be measured. The lower portion in each type of depthometer incorporates an oil bath, in which all the moving parts are immersed — a refinement aiding in no small measure the outstanding features of the system—reli- ability and automatic action for indefinite periods. Coke Fuel for Motors.—A new type of steam wagon has, as a special feature, facilities for automatic coke firing, so that coke may be used more conveniently. It is proposed to adapt this type of chassis to public omnibus service, and this tendency might be encouraged with advantage to the national economic interests. Tests extending over 12 months in actual service have proved this type of omnibus and wagon to be quite practicable, and, moreover, decidedly economical. Based upon the report of the Royal Automobile Club Technical Committee, the average coke consumption on a run of 219 miles with a load of 2 tons 15 cwt. was about 4 lb. per mile. At 25s. per ton, over 7 lb. of coke is obtainable for Id. Thus very considerable economy in fuel cost may be realised by adapting exist- ing omnibuses to the use of coke as fuel in place of imported oil or petrol. The daily coke consumption of a ’bus operating in the London area is about 4 cwt., and the estimated daily consumption of a full normal service of 4,000 ’buses would be about equal to the coke production of one of the largest London gas works.