engineers to the undertaking are Messrs. Sir Douglas Fox & Francis Fox, London. The contractors are Messrs. Holme & King, Liverpool. The author is the Resident Engineer. SATURDAY, SEPTEMBER 14. The following Reports and Papers were read : 1. First Report on Standardising.-See Reports, p. 497. 2. Report on Coast Erosion.-See Reports, p. 352. 3. Dredging Operations on the Mersey Bar. The paper commences with a short account of the physical and geographical features of the river Mersey, tracing its course from the junction of the Goyt with the Etherow, near Stockport, to the mouth of the river. A more detailed description is given of the course of the river where it enters Liverpool Bay, and the form and character of the main channel are explained. The bar is next considered, its former condition described, and the positions of the main channel and of the bar at the outlet of the main channel are shown to be by no means permanent, but to have both altered considerably within quite recent times. The great inconvenience of the bar as a cause of delay to modern navigation is discussed and the urgent necessity for amelioration is shown. Dredgings operations which have been undertaken at New York and at the mouth of the Mississippi are then touched upon, and a comparison is made between the work done at these places and that in progress at the Mersey Bar. After describing the position of the dredged cut, which is also shown by diagrams, an account is given of two steam hopper barges which were first fitted up with sand pumps and used for the purpose of dredging a deep cut across the Mersey Bar, their capacities, rates of loading, suction tubes, hoppers, and general characteristics are fully described, as is also the variable nature of the material which they are engaged in removing. An account of the quantity of material removed by these dredgers is then given and a description of the new and more powerful dredger, the 'Brancker,' which was built in consequence of the successful results achieved by the smaller ones, is entered upon. With regard to the 'Brancker' the form and dimensions, fittings, contract conditions, work done, and the proportion of the whole time available for working are fully dealt with. The fitting up of the steam tender the Alarm' as an 'eroder,' with the object of dealing exclusively with the fine mud on the outer face of the bar on ebb tides, is next described. The material found on the bar is then analysed. Sections taken across the bar in 1890, 1893, and 1895 are compared, and an account is given of observations of the rate of flow of neap and spring tides both previous to and during the present operations, while the paper closes with an expression of the author's views on the general theory of the formation of river bars, and the advisability of further increase of the dredging plant. 4. On Carbonic Anhydride Refrigerating Machinery. By E. HESKETH. 5. On the Deodorising of Sewage by the Hermite Process. By J. NAPIER, F.C.S., Public Analyst for County of Suffolk. This process consists of passing an electric current obtained from a dynamo through sea water or a solution containing magnesium and sodium chlorides, whereby a portion of the chlorides is converted into hypochlorite, a substance which disinfects, deodorises, and bleaches similarly to the active ingredient of bleaching powder, viz., calcium hypochlorite. This solution is called the electrolised or 'hermite' solution, and may contain from half to one gramme of active chlorine per litre. The author gives a brief history of the sewering of Ipswich during the last twenty years, showing the present system, particularly the position of the main sewer as it passes through the town to the outfall. The deodorising effects of the electrolised (hermite) solution on sewage, especially upon that in the main sewer of Ipswich, are dealt with, and the results of trials made in August and September 1894 and in June, July, and August of this year are given. The installation was at full work during the meeting of the Association. Those interested in the electrolysis of sea water and its effects on sewage were invited to visit the works. MONDAY, SEPTEMBER 16. The following Papers were read :- 1 The Modern Application of Electricity to Traction Purposes. Introductory. Sketch of progress made during the past decade; introduction of the under-running trolley and earth return; adoption of electrical motive power by the West End Street Railway of Boston, U.S.A., in 1888; in 1890, 2,523 miles of electric tramways in America; rapid increase in mileage and equipment in the United States; statistics and financial statement; first prominently successful line in Europe at Halle, Germany, in 1891; statement of present European installations and of electrical tramway construction now under contract. General and Descriptive.--The especial adaptability of electric traction to tramways and light railways; but three methods of electrical power transmission practically employed: (1) by elevated conductors with trolley contact; (2) by subsurface conduit-contained conductors-and (3) by surface or third rail conductors; the former by far the most efficient and successful and in most extensive use; objections to the overhead wire and compensating advantages. Parts of an Electric Tramway Installation.-Latest machinery apparatus and methods of construction. (a) Power, Plant.-Approved engines, dynamos, and accessories; general use of compound-wound machines; direct coupled generators for large units; importance of automatic circuit breakers; power required; reserve; utilisation of accumulators. (b) Motors and Gearing.-Specific requirements for exacting service; general design; results of tests. (c) Regulation and Control.-Construction and operation of the series parallel controller; its economy as contrasted with former methods; speed regulation. (d) Motor Trucks.-Essential points of construction; four-wheel, bogie, and radial trucks; safety appliances; brakes, fenders, sand-boxes, lightning arresters, &c. (e) Trolleys.-For cars with and without roof seats, and for varying methods of trolley-wire suspension; wheel and scraping contacts; modern pivotal trolleys. (f) Overhead Line.-Description of material employed; poles, trolley-wire, insulators, span-wire, lightning arresters, &c.; methods of suspension adopted on British and Continental lines; feeders; double-conductor construction. (g) Return Circuit. Its importance; supplementary return feeders; bonds and method of bonding; electric welding. Notable Installations.-European and American; three-phase at Dublin, Sacramento, and Portland; three-wire system; water-power; 'light railway,' mining, and other services. Application to Railway Service.-City and South London Railway; Liverpool overhead; Chicago and New York Elevated Railways; branch lines and suburban service in connection with steam lines; Baltimore and Ohio Railway Company's 95-ton locomotives. Conclusion.-Economic results already attained; probable extension and development. 2. An Improved Portable Photometer.1 By W. H. PREECE, C.B., F.R.S., and A. P. TROTTER, B.A., A.M.I.C.E. The authors begin by defining what is meant by illumination. When light falls upon a surface that surface is said to be illuminated. The illumination depends simply upon the light falling on the surface, and has nothing to do with the reflecting power of the surface, just as rainfall is independent of the nature of the soil. It depends also on the cosine of the angle of incidence. The lighting of streets and of buildings may be specified by the maximum and minimum illumination. The primary purpose of an illumination photometer is to measure the resulting illumination produced by any arrangements of lamps irrespective of their number, their height, or their candle-power. The authors allude to the illumination photometers of Weber and Mascart,3 Preece's first photometer, the authors' modification," and Trotter's further modification, which was used for measurements and photometrical surveys of streets and public buildings in London, 1892. The new instrument (see figure above) is a box, on the upper surface of which is a diaphragm of white card painted with a whitewash of magnesia and isinglass. It has one or more star-shaped perforations. Published in full in the Electrician, September 20, 1895. 2 Elec. Zeit. 1884, p. 166. Proc. Roy. Soc. xxxv. p. 39, 1883. 6 Proc. Inst. C.E. cx. p. 105. 1895. 3 Bull. de la Soc. Inst. des Elec. 1888, p. 103. 5 Proc. Inst. 3, 8, cx. p. 101. 3 F Immediately below it, within the box, is a white screen capable of adjustment at different angles and two small electric lamps of different candle-power, either or both of which can be used. A portable secondary battery is used to supply them with current. The illumination of the hinged screen inside the box varies approximately as the cosine of the angle of incidence of the light from the electric lamps upon it. A handle with a pointer moving over a graduated scale is connected to the screen with a system of levers, and the inclination is so adjusted that the illumination of the screen is equal to that of the perforated diaphragm, the perforations seeming to disappear when this balance is affected. The illumination can then be read off on the scale in units of the illumination due to one standard candle at one foot distance. The object of the levers is to give an open and convenient scale. The scale is graduated by experiment, and does not depend upon the cosine law. The colour difficulty, where are light or daylight is to be measured, is reduced by the use of a yellow-tinted diaphragm and a blue-tinted screen, the tints being selected so that the readings are the same as the mean of a large number of measurements made with white screens. By means of a graduated quadrant and a gnomon the angle and the cosine of the angle of incidence of the light from a lamp may be measured, and rules are given for deducing the height of the lamp and the slant height, and hence the candle-power of the lamp. 3. On Storage Batteries. By H. A. EARLE. The author traced the history of storage batteries from the time when Gautherot, in 1801, obtained secondary currents from silver and platinum plates which had been used in a voltameter to decompose a saline solution. Ritter, in 1803, was the first to make a secondary battery, in which he employed plates of gold separated by cloth or paper, moistened with a saline solution; and though he employed various metals, including lead, the secondary currents he obtained were only of short duration, and the batteries of only scientific interest. It would naturally be presumed that he would have noticed increased effects when using lead, but we find that he used salt water and not an acid solution, and on this account chloride of lead was formed, which is scarcely soluble and is a bad conductor. De la Rive in 1826 obtained secondary currents from platinum plates in a voltameter filled with water, and he closely approached the elements of our present storage cells when, among his many experiments, he used in a primary battery a platinum plate covered with a film of peroxide of lead, and a zinc plate immersed in an acid solution. The first powerful storage battery was introduced by Planté in 1860, but the method employed for its formation was too long and costly for practical purposes. Faure, in 1881, reduced this long process of formation by applying lead oxide in the form of a paste to the surfaces of the plates, but the adhesion was insufficient, and the life of the cells was too short to give them commercial value. Swan realised that the active material required a better mechanical support, and introduced a plate of grid form, the interstices serving to retain the material; and this frame, combined with the Faure pasting, was the origin of the plates largely used in this country and elsewhere. The monopoly that existed for the manufacture of this plate caused other makers to turn their thoughts to the plain lead plates, and such great advances have been made both in their manufacture and method of formation, that it is rapidly replacing the pasted form. A type that differs greatly from the solid lead plate, but which is not pasted, is the chloride plate, in which the material to become active is a mixture of chloride of lead and chloride of zinc cast into small tablets, which are framed by casting antimonious lead around them under high pressure. The subsequent elimination of the chloride and zinc leaves a porous structure of pure lead of a crystalline nature, of good conductivity, and with a large surface exposed to the electrolyte, the result being a large capacity for a given weight, and for the space occupied. Omitting the question of cost, the chief points to be considered in connection with accumulators are-the chemical action, the mechanical construction, and the proper treatment of the cells when made. The theoretical value of lead peroxide is 4:44 grammes per ampere hour, or, roughly, one pound is the equivalent of 100 ampere hours. Presuming that the positive and negative plates were identical, the value would be approximately 50 ampere hours for one pound of peroxide and spongy lead. As a matter of fact, the highest capacity plates yield only about seven ampere hours per pound of positive and negative plates, or sixteen ampere hours per pound of peroxide and spongy lead, due to the facts that a conducting frame of considerable weight has to be employed, and to the impossibility in practical working of reducing the whole of the peroxide. To obtain the best results for a given weight the frame must be reduced to a minimum consistent with the necessary strength and conductivity, and the distribution of the peroxide must be such as to admit of the perfect circulation of the electrolyte, and its penetration throughout the mass. The behaviour of cells under various conditions is most interesting, and from the curves that can be plotted we can readily study the effects due to different rates of charge and discharge, to the penetration and strength of the electrolyte, and to the ratio of the weights of the positive and negative plates. There is a given rate of charge which is most suitable to each type of cell, mainly due to the disposition of the active material, to its thickness, and to the method of its production, namely, whether it has been mechanically applied or electrolytically produced. Most of the effects of varying rates of charge can be ascertained from the resultant discharges, but discharge curves have nevertheless characteristics of their own, which are to a great extent unconnected with the conditions of charges. A series of curves was exhibited to the Section which gave the capacities of seven types of plates at present in use; the yield was given in ampere hours per pound of positive and negative plates, the weight of one positive and one negative being taken in each instance; the variation in capacity for high and low rates of discharge was also shown. The striking point in these curves is the great variation existing in the various types of plates now in use, but this can be explained to a great extent, for the heavy solid plates, the active material of which is formed out of the plates themselves, must have a large reserve of weight to give them life, while pasted plates, or plates with a large area, fall higher on the curve. One plate greatly exceeds all the others in capacity, and this is due to the nature of the active material, which permits the penetration of the electrolyte throughout the mass. Regarding the voltage of a discharging cell, this varies greatly, and is dependent upon the rate of discharge, the strength of the electrolyte, and other causes. In considering this question, it will not be out of place to draw attention to conditions frequently met with in specifications for storage batteries. In some instances a given percentage in fall of voltage is allowed; in others the voltage per cell is fixed to a hundredth of a volt, above which limit it must give the specified capacity. This type of specification is, as a rule, most unsatisfactory, for at what point does our initial voltage start? On open circuit ? Immediately on closing the circuit, or five minutes afterwards? Further, may the cells stand for half a day after charging before the discharge is taken? The best way to meet this latter case is to take the first reading of voltage after the cell has commenced discharging, and when 3 per cent. of the specified discharge period has elapsed. The most satisfactory specification to all concerned is for the amperes to be specified, and the time for which the discharge is to be maintained, the voltage of the complete battery at the end of the discharge being also given, the number of cells being omitted; this would require for a low voltage discharge per cell an increased number of cells, but a decreased number of plates, or vice versá; and the author finds that this would not admit of the individual cells being worked to too low a voltage, and that the purchaser would obtain exactly what he requires at the lowest price. |