SECT. III.-BRIEF ABSTRACTS OF PAPERS IN SCIENTIFIC TRANSACTIONS AND PERIODICALS.

The object of these Abstracts is to indicate the nature and scope of the more important information appearing in current engineering literature, and where it is to be found.

Fixation of Atmospheric Nitrogen.-L. L. SUMMERS.-Proceedings of the American Institute of Electrical Engineers, New York, 1915, vol. 34, pp. 337-371.-The theoretical thermo-chemical questions involved in the fixation of nitrogen are considered, and it is shown that a purely thermal process, such as that adopted in the Birkland Eyde apparatus, has an efficiency not exceeding 4.3 per cent., the balance being required for heating that portion of the air which is not utilized. A thermo-chemical process, such as the Serpek or the Haber catalytic, is far more efficient. A tabular comparison of the power-requirements of four different types of processes is given.— H. R. S.

Cyanamid Works at Niagara Falls.-Engineering News, New York, 1915, vol. 73, pp. 16-21.—Owing to the demand for nitrogen in an available form for agriculture, the production of cyanamid has become an important industry. The process here described is the Frank and Caro system, in which calcium carbide, when raised to a temperature of 1,200° C., combines with nitrogen, forming calcium. cyanamid, the nitrogen being obtained from the atmosphere by the fractional distillation of liquid air.-C. O. B.

Triangulation for Economical Surveys.-K. S. KLINGENBERG. -Teknisk Ukeblad, Christiania, 1915, vol. 62, pp. 203-204.-The Author deals with the work of the State Survey Department of Norway in connection with a system of triangulation arranged to serve as a basis for economical detail surveys at subsequent periods. He describes in detail the instruments used, the methods and calculations adopted, and gives a typical diagram of the triangulation. -L. S. Z.

Colour of Illuminants.-L. A. JONES.-Transactions of the Illuminating Engineering Society, New York, 1914, vol. 9, pp. 687-709.— Monochromatic methods of determining colour and the instruments used are described. White light is defined as that of the sun at noon. Sunlight was reflected from a block of magnesium carbonate, first passed through a nicol prism, then through a collimating lens, after which it was partially reflected on to the middle of

the field of a telescope. The coloured light to be added to make a match was obtained from a Nernst glower dispersed by a constant deviation prism, and its wave-length was determined by calibration. The light to be analysed passed through a nicol and was then reflected into the telescope for comparison. The various colours of the Nernst glower, tungsten, and carbon lamps, etc., were determined when run at different wattages.-H. R. S.

Safeguarding the Eyesight of School-Children.-M. LUCKIESH. -Transactions of the Illuminating Engineering Society, New York, 1915, vol. 10, pp. 181–202.-Data are given showing the increase of short-sightedness from class to class, the cause being ascribed to glare from windows, blackboards, glazed paper and artificial sources of light. The factors influencing vision are discussed. As regards illumination, it should not be less than 2.5 foot-candles, and rules as regards direction of light, glare and types of reflection are given. Recommendations as to the best arrangement of natural light from windows are studied, and as regards artificial lighting, semi-indirect is recommended. Examples, photographically illustrated, show good and faulty arrangements.-H. R. S.

Artificial Daylight-Its Production and Use.-M. LUCKIESH and F. E. CADY.-Transactions of the Illuminating Engineering Society, New York, 1914, vol. 9, pp. 839-872.-Nitrogen-filled lamps give a whiter light when run at the same lumens per watt than vacuumlamps. From a diagram of the luminous intensity for wave-lengths of 0.44 to 0.68 for blue skylight, sunlight and various tungsten vacuum-lamps, the characteristics of the colour-screen required to produce white light can be obtained. The radiation from a tungsten lamp may be regarded as a light of the same quality as sunlight on which has been superimposed a yellow light. The ratio of the sunlight-component to the total light is defined as the "daylightefficiency," and varies with the lumens per watt at which the lamp is run. The problem of determining the glass colour-screen which would produce artificial blue skylight is discussed, and a method is developed showing that transmission and thickness are connected by a straight-line law.-H. R. S.

Development of Daylight-Glass.-E. J. BRADY.-Transactions of the Illuminating Engineering Society, New York, 1914, vol. 9, pp. 937960. The principle on which " Daylight-glass" acts is to subtract by transmission certain rays so that the remainder shall give a daylighteffect. A figure shows the energy-distributions on wave-length base for average daylight and for a Welsbach mantle. The transmission for ideal daylight is deduced and charts are given for the transparency of various glasses. The direction to be followed in preparing a suitable daylight-glass is thus obtained. A chart of the energy-distribution of the light obtained from a nitrogen-filled lamp after passing through a glass so developed shows a fairly close coincidence with the energy-distribution of daylight.-H. R. S.

Lighting of Rooms through Translucent-Glass Ceilings.-E. J. EDWARDS.-Transactions of the Illuminating Engineering Society, New York, 1914, vol. 9, pp. 1011-1020. The result of lighting special rooms by light passing through translucent ceilings is not always satisfactory, probably owing to want of data. To eliminate the "spotting" effect, the glass should be diffusing, and the ratio of lamp-spacing to the distance of the lamp from the glass depends on the kind of glass, it being suggested that for a given glass the ratio of these two dimensions is a constant- -a rule confirmed by tests described. Photographs show the effects of various patterns of glass. An apparatus for measuring the efficiency of transmission is described, with a Table of results.-H. R. S.

Planning for Daylight and Sunlight in Buildings.-L. B. MARKS and J. E. WOODWELL.-Transactions of the Illuminating Engineering Society, New York, 1914, vol. 9, pp. 643-686.-The broad principles of providing adequate sunlight and daylight in buildings are dealt with. To determine the amount of daylight through a particular window it is necessary to obtain data as to the sky-obstruction, and a suggested photographic method is given from which a sky-line is obtained. A study was made of the new County Court House, New York, by means of a cardboard model on which was placed a wire frame representing the celestial sphere, with hour-marks from which the direction of the sun's rays-represented by a parallel beam from a small electric lamp-could be determined at any moment. In this way the penetration of sunlight into various parts of the building and the shadows could be graphically obtained. An instrument devised for the purpose is also described and illustrated.-H. R. S.

Present Practice in the Use of Tungsten-Filament Lamps for the Lighting of Metal-Working Plants.-A. L. POWELL and R. E. HARRINGTON. Transactions of the Illuminating Engineering Society, New York, 1914, vol. 9, pp. 814-838.-The method of illumination of a large number of different kinds of metal-working shops is given, in each case with particulars of the class of work done and the size of lamp, type of reflector, spacing, and watts per square foot which have been found satisfactory. Photographic reproductions of the lighted shops enable a good idea to be obtained of the result. The size of the lamps used varies considerably, in general 100-watt lamps for the smaller shops to 1,000-watt lamps for rolling-mills. The watts per square foot vary between 0.40 and 0.70.-H. R. S.

Factory-Lighting.-O. R. HOGUE and A. O. DICKER.-Transactions of the Illuminating Engineering Society, New York, 1914, vol. 9, Pp. 974-989.-The experience gained in factory-lighting by the Edison Company of Chicago is detailed, with a form of contract to be signed by factory customers. A type of lamp-reflector, chosen as a standard after many trials, is a shallow white-enamelled bowl of steel, and is made in three sizes. A polar photometric curve [THE INST. C.E. VOL. CC.]

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shows the distribution obtained with this reflector. A Table shows the units installed and their size, the watts per square foot, the ceiling-height and the hanging height of fixture for a large number of different kinds of shops.-H. R. S.

Recent Advances in Indoor Gas-Lighting.-C. W. JORDAN.— Transactions of the Illuminating Engineering Society, New York, 1914, vol. 9, pp. 873-894.-To investigate the cause of the deterioration of gas-mantles, microphotographs of the fibres, reproductions of which are given, were taken after the lamps had been burning for 500 up to 6,680 hours. It is suggested that an internal change takes place, and this can be observed by transmitted light showing the production of a crystalline structure. Several arrangements adopted for igniting a gas-burner at a distance are described; none, however, seem absolutely satisfactory.-H. R. S.

Analysis of Requirements for Modern Street-Car Lighting.L. C. DOANE.-Transactions of the Illuminating Engineering Society, New York, 1915, vol. 10, pp. 82-100.-The general rules for carlighting are considered. To prevent eye-strain no lamp should be used without a shade, and a section is given of a prism-reflector in which the lamp is so placed that the direct rays are cut off at 20°. This screening-angle was determined by directing a beam of light into the eye at various angles. Tables give particulars of illumination and costs for car-lighting.-H. R. S.

Practical Study of Car-Lighting Problems.-W. G. GOVE and L. C. PORTER.-Transactions of the Illuminating Engineering Society, New York, 1915, vol. 10, pp. 227-252.-Exhaustive tests were made to obtain the best form of illumination for the 600 cars recently built for the New York Subway. Direct, semi-direct and indirect lighting were tried, as well as different sizes of lamps and kinds of fittings. Photometric and other tests were made, and the results obtained are plotted, showing the intensity of light at seventeen" stations" at different points along the car. The effects produced are also shown by photographs. The car was painted a creamy white, which greatly improved the lighting. Based on these tests, it was finally decided to place fifteen 56-watt bowl-frosted tungsten lamps down the centre of the ceiling, supplemented by six 10-watt emergency-lamps.-H. R. S.

Street-Lighting in Chicago.-P. E. HAYNES.-Transactions of the Illuminating Engineering Society, New York, 1915, vol. 10, pp. 281-288.-After a short historical account of the various stages in the lighting of Chicago, dating from the time of "pine-knots" to the electric arc- and incandescent-lamps, some of the more interesting engineering problems involved are considered. The method adopted for selecting the type of arc-lamp is described. The lighting of subways under the elevated railways was especially studied, and two methods were tried. Photographs show the effect of both. Polar curves are given of the various types of lamp adopted.-H. R. S.

New Standard-Light Source.-L. A. JONES.-Transactions of the Illuminating Engineering Society, New York, 1914, vol. 9, pp. 716733. An acetylene-burner used as a standard-light source consists essentially of a cylindrical flame, a portion only of which is viewed through a rectangular window formed in a metal cylinder, the edges of which extend inwards to within two millimetres of the flame, to avoid the errors due to parallax. Comparisons were made by means of electric standard-lamps standardized by the National Physical Laboratory. Measurements were made at different pressures and with the window placed at different heights along the flame.-H. R. S.

Incandescent Headlights and Projectors.-P. S. BAILEY.Transactions of the Illuminating Engineering Society, New York, 1915, vol. 10, pp. 271-280.-The gas-filled tungsten lamp with focusingtype filament is well suited to projectors. The Author, after testing several combinations, concluded that the parabolic reflector is the best. A description is given of the method of spinning a parabolic reflector in thin copper sheet, and it is stated that this metal is better than brass, especially for a steam-road service. Various locomotive head-lamps are shown. A curve is given of the apparent candle-power at various distances from the centre of the beam with a 6-volt 36-watt focus-type tungsten lamp.-H. R. S.

Searchlights.-C. S. MCDOWELL.-Proceedings of the American Institute of Electrical Engineers, New York, 1915, vol. 34, pp. 195208. This Paper consists principally of a comparison of the Beck 46-inch searchlight with the 36- and 60-inch U.S.A. naval apparatus. Various tests, to which the mirrors and arc-lamps are subjected, are described. Searchlights are best compared by finding the footcandles at various distances from the centre of the beam at a given distance from the light. The greater the foot-candles on the centre line and the more rapid the reduction to each side the better. Several plots of such tests are given, showing the superiority of the Beck 46-inch searchlight.-H. R. S.

Photometry of Gas-filled Incandescent Lamps.-C. H. SHARP.Transactions of the Illuminating Engineering Society, New York, 1914, vol. 9, pp. 1021-1032.-It has been found that the watts consumed and the candle-power of nitrogen-filled lamps depend, when taking a photometric test, on the speed of rotation of the lamp. The spherical-reduction factor depends on the shape of the filament and varies during the life of the lamp. The mean horizontal candlepower decreases less rapidly than the mean spherical candle-power, hence the usual rating of lamps by mean horizontal candle-power cannot be applied in the case of gas-filled lamps. The Author suggests that the introduction of these lamps furnishes an opportunity of adopting a more logical basis of rating, namely, "lumens per watt."-H. R. S.