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The telegraph department has obtained batteries from various firms, of which the following are the chief:-the Hagen Accumulator Works, the Geluhausen Company, the Pollak Company, the successors of W. A. Boese & Company, the Gulcher Company, and Oskar Bolle; and the Author then describes the various forms of plates supplied by the makers, which are shown in illustrations. The rules for inspection before acceptance are given, but it is distinctly stated that the cells are as a rule not tested electrically. The arrangement of the cells and stands is then described; connections between plates and between cells are now made by lead burning, and seldom by bolts. The Pollak Company use a special method of connection, as they employ an alloy, consisting of 15 parts lead, 4 parts mercury, and 1 part antimony, which is melted by means of a Bunsen burner. In the telegraph department the cells are charged either from a dynamo or from copperzinc cells, but the latter are used only if the former is not available. Diagrams are given showing the methods of arranging the cells and the connections for charging, resistance, etc. A line-voltage in the public supply of 100 to 120 volts direct current seems to be the most suitable arrangement.

For telegraphic purposes a steady working-current of 0.002 ampere in the line-wire is necessary, and, therefore, the battery must be calculated to supply this current, multiplied by the number of lines it is required to feed. Copper cells are only used to charge the secondary batteries up to 13 or 15 ampere-hours' capacity; above this capacity either a dynamo or the public supply mains are employed. The articles give a good general idea of the present condition of the employment of batteries in the German telegraph department.

E. R. D.

Measurement of the Capacity of Submarine Cables.
DEVAUX-CHARBONNEL.

(L'Électricien, Paris, 1905, vol. xxix. pp. 243–48.)

The Author describes an improvement on the Thomson method of measuring the capacity of submarine cables. The battery has one terminal put to earth while the other is connected through a key to one plate of a condenser. The other plate is connected to a two-way switch, by means of which that plate is put to earth either through the cable or through a ballistic galvanometer. The cable is put in the circuit first, and when it has taken up its charge the key is switched over to the galvanometer. The condenser has now the free E.M.F. of the battery applied to it instead of, as formerly, the difference between that E.M.F. and the potential at the insulated end of the cable. A charge therefore passes through the galvanometer and is measured. Another measurement is made by operating on the condenser alone. Three equations are thus

obtained which give the capacity of the cable in terms of that of the condenser and of the deflections of the galvanometer. The Author indicates the advantages of the method and gives results of actual trials.

W. C. H.

Worm Gearing in Electric Tramcars. H. SOMACH.

(Le Génie Civil, Paris, vol. xlvi. pp. 303-304.)

In order to obtain the maximum power per unit weight of motor the speed of rotation must be high, and the reduction of this to the comparatively low speed of the car-wheels has always presented some little difficulty. Worm gearing possesses the great advantage that a high degree of reduction in speed can be obtained with a single worm and wheel, whereas, if spur gearing, ropes or belts were employed, a multiplicity of moving parts would be inevitable unless the degree of reduction were small. The excessive loss due to friction in worm gears has frequently been spoken of, but with properly designed gearing the efficiency is by no means low. A curve is reproduced to show, inter alia, the efficiency of a worm drive operated by an electric motor of 40 HP. at all loads, from which it is seen that when working at load upwards the efficiency, which is singularly constant, averages about 90 per cent. The wear in this gearing after years of work was found to be inappreciable. Hitherto, when worm gearing has been adopted for tram-cars the motor has been supported directly by the axle, and, owing to the shocks then caused by the unevenness of the road, trouble has frequently been experienced and spur gearing has then sometimes been substituted for the worm. The Oerlikon Company has recently made a new departure by attaching the motor to the framing of the bogie, the springs thus intervening between it and the road-wheels. The coupling with the worm is then effected by a pair of universal joints. The worm is triple-threaded and has a pitch of 120 millimetres (4.7 inches); it is made of hardened steel, the teeth of the wheel being of phosphor bronze. The reduction in speed is 1 to 12. The power on each car is derived from two motors running at 1,200 revolutions per minute, and weighing 300 kilograms (660 lbs.) each. If transmission by single spur gear were adopted, the motors would run at 500 revolutions per minute, and would weigh each 650 kilograms (1,430 lbs.). Stress is laid on the advantage of having the motor hung from the framing of the bogie, thus avoiding the sudden jars due to the imperfect road.

I. C. B.

[THE INST. C.E. VOL. CLXII.]

2 ң

Resistance of Concrete to Pressure and Shearing.

Professor MÖRSCH.

(Schweizerische Bauzeitung, vol. xliv. p. 307. Figs.)

The Author has made a large number of practical experiments upon specimens of concrete in the form of ordinary concrete, and also of reinforced concrete. This article deals first with the resistance to torsion of concrete cylinders, and the Author shows that the fracture will take place upon a spiral rising at an angle of 45o, and at right angles to the direction of the greatest torsional stress. The specimens tested are illustrated from photographs, and appear to be formed with hexagonal ends to facilitate torsional

tests.

Tables of the results are given in the original, and then tests are described of hollow cylindrical specimens with spirally wound reinforcement. The latter part of the Paper deals with experiments on the adhesion of the concrete to the iron, and the Author says that, although these experiments are easy to make, few results are available; he remarks that Prof. Bauschinger made tests in Berlin some time ago, and stated that the adhesion was about 640 lbs. per square inch of surface in contact, and this result has since usually been quoted in writings on the subject. In 1894 de Tedesco made similar experiments with concrete only 6 days old, and the iron rods were 0.234 to 0·468 inch in diameter, and the adhesion varied from 285 lbs. to 355 lbs. per square inch of the surface in contact.

The Author made experiments on this subject with rods 0.78 inch in diameter, and with concrete 5 months old obtained an adhesion of 540 lbs. per square inch of surface.

In the original there are numerous tabulated results of the various tests which cannot be usefully abstracted.

E. R. D.

Buckling Strain Tests on Round Rods with Clamped Ends.

Professor B. KIRSCH.

(Zeitschrift des Vereines deutscher Ingenieure, 1905, vol. xlix. pp. 907-15.)

Theoretically the clamping of round rods at both ends should increase the resistance to buckling fourfold, in comparison with the resistance offered when they are mounted between points. The tests performed by the Author, however, show that with slender rods the maximum increase is only threefold, and that in moderately slender rods the increase is not more than 13 Another result of the tests is that in the case of per cent.

test-rods 5 to 40 inches in length, with one free end, the other clamped, the point of maximum deflection is 1 to 2 inches nearer the clamped end than it should be theoretically. A further point of some importance is that, with test-rods mounted between points, a very slight eccentricity suffices to greatly modify the results of the test. For instance, an eccentricity of -inch may reduce the apparent buckling strength by rather more than one-half its true value. For this reason it is considered desirable always to calculate on an eccentricity of inch, and to disregard the effect of clamping altogether. The Author considers that for practical purposes the buckling load is that under which the rod is deflected by 1 per cent. of its length, this load allowing a twofold margin of safety.

The tests were made in an Emery machine, the deflection being measured by means of a horizontal scale, with a small pulley at one end, from which was suspended a plummet that could be lowered so as to touch the nearest edge of the test-rod. The reading obtained is thus direct, and no calculation is needed. The Paper is illustrated by figures and diagrams.

C. S.

Injection of Liquid Cement to stop Cracks and Leaks.

AUGUST WOLFSHOLZ.

(Gesundheits-Ingenieur, Munich, 20 May, 1905, p. 234–36.)

It often becomes necessary in cellars and basements and in underground rooms to render the walls sound and water-tight, and the Author states that this may readily be done by drilling a series of holes through the walls and injecting liquid cement by means of air-pressure. Diagrams are given to explain the requisite apparatus, but a simple hand force-pump with an india-rubber pipe to connect it with a vessel containing the cement, furnished with a delivery pipe and jet, is all that is necessary. An illustration shows the process of rendering a damp tunnel water-tight by means of numerous holes drilled through the crown, into which the cement is sprayed. Another diagram explains the method of stopping the inflow of water from a high-level culvert into the pier of a bridge. It is pointed out that where the flow of water is considerable it may be advisable to render the cement quick-setting by adding to it a solution of soda, which causes it to set in a few minutes. This method is advocated as furnishing an excellent plan for keeping back damp and wet in all kinds of underground buildings, and it is thus very easy to produce a layer of cement at the back of the work, where it is safe from injury and abrasion.

G. R. R.

Organization and Methods of a Modern Industrial Works.
J. WILMER HENSZEY.

(Journal of the Franklin Institute, Philadelphia, December, 1904, pp. 401–409.) The Baldwin Locomotive Works in Philadelphia employ about 15,500 men, who are divided among twenty departments. The executive force consists of one superintendent, four assistant superintendents and twenty foremen. The works are divided into two parts: the eastern division embracing all shops east of Fifteenth Street, and the western division all shops west of that street, and the new shops located in Twenty-sixth, Twenty-seventh and Twenty-eighth Streets. Each division is in charge of an assistant superintendent, who works in conjunction with the foreman in his division. In the eastern division the most important shop is the erecting shop, which employs about 2,500 men and has a capacity of fifty finished locomotives every week. To operate this department there are one foreman, two assistant foremen, and twenty track foremen, each of the latter being a specialist in a certain line, such as erecting, valve-setting, testing, etc., and having charge of the contractors and men working under his supervision. The same system of contract or piece-work is employed in every department throughout the works; it is arranged as follows:Every department is a factory manufacturing a certain number of locomotive parts, the exact time and expense involved in manufacturing these parts are known, the contractor is allowed a certain amount, and he gives out the work piece-work to the men at a lower rate, the difference being his profit. When a man is taken on at the works, whether unionist or not, he has to abide by the rules and regulations, or he is dismissed. The difficulty of procuring suitable skilled workmen has led to the revival of the old apprenticeship system. The apprentices are divided into three classes-first, second and third. To be a first-class apprentice a boy must be 17 years old, and must have had at least a grammar-school education. He serves 4 years, during which time he is only allowed to stay at one class of work for 3 months, and is moved from department to department till he covers the entire plant. He is obliged to attend night-school two nights a week, taking up a special course in higher mathematics and mechanical drawing. He is paid $3.00 to $6.60 per week during apprenticeship, and on completion of his time receives a certificate and a bonus of $250. A second-class apprentice must be a highschool graduate, and serves 3 years on the same lines as the firstclass apprentice; he is paid rather higher wages and a smaller bonus on completing. A third-class apprentice must be a graduate of a recognized technical school; he serves 2 years, does not take a night course, and is paid higher wages but receives no bonus on completing his time. There are at present 400 to 500 apprentices of the several classes, and the system has proved beneficial to the works.

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