NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

New Zealand Herald, Volume XXVIII, Issue 8538, 11 April 1891, Page 4 (Supplement)

NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

THE PATHOLOGICAL EFFECTS OF THE ELECTRIC LIGHT.

Attention has been drawn to the advisability of the adoption of early remedial measures by those who are suffering from the effects of a too long exposuro to strong electric light. The '' tired " sensation in the optic nerve, which such exposure causes, and the local inflammation which accompanies it, are both due to the fact that-the luminous waves proceeding from a powerful electric lamp are of very great intensity. Tho general symptoms induced in the eyes of people who have been exposed to the glare of unprotected lamps for too long a time are :—l, Transient irritability of the retina ; 2, local inflammation ; 3, tears and " flashing "of light before tho eye; 4, incipient paralysis of the eye. Usually people experience sensations which are analogous to those which are felt when particlos of foreign matter are present beneath tho eyelid. In order to prevent the sight being permanently injured, it is necessary to adopt hygienic shades, though these do not act thoroughly in reducing the intensity of the luminous waves*. Rest must be sought and tho pain relieved by the application of cold water compresses. When the pain is almost unbearable—a calamity frequently suffered by those who have been exposed for many hours a day to the glare of powerful lamps — a medical man may relieve it by the injection of cocaine and atropine. The French call this peculiar malady "electrical sunstroke." FOAMING IN BOILERS.

When boilers are new and first used, they are liable to foam, in consequence of grease or oil left in them during their manufacture. The simplest remedy for this is to put from one-half to one pound common washing-soda in tho boiler when first filled with water. After steam has been raised and the soda has neutralised tho oil anil grease, draw tho fires, and when the pressure of steam has been reduced to not exceeding five pounds, blow out the boiler, then fill with fresh water, adding a very small quantity of soda to neutralise any grease remaining within tho boiler. The general cause of boilers foaming is using the steam faster than tho fires are generating it, as any boiler can be caused to foam by drawing the steam from it faster than it is beinggenerated. The remedy in this case is to close tho throttle so as to reduce the quantity of steam discharged in proportion to tho amount being produced, increase the fire so as to make more steam, and tho quantity available for service will be in accordance, without danger of foaming.—Safety Valve. A PECULIAR PHENOMENA IN' WELDING.

Iron is now plated with nickel by pressure between rolls at a welding heat, the nickel being recovered from the clippings and shearings of the plates by the action of dilute sulphuric acid at a temperature of 55" C.; the iron is dissolved and tho nickel

is obtained in the form of thin sheets as it was melted upon the iron. The operation is complete when the evolution of hydrogen ceases—even fresh acid, at the same temperature, has practically no effect. But though the separation of tho two metals is apparently perfectly made, a curious fact is noted, namely, that when the residual nickel is chemically examined it is found to differ from its original composition, the amount of iron present being notably increased. For example, in a nickel containing originally only "09 per cent, of iron, 2 per cent, more was found when it was recovered from the plate cuttings, and, even by a long-continued treatment) with dilute acid, the iron could not be sensibly reduced. This peculiar behaviour* it is believed, points to the possibility of positive chemica combination taking place between the metals, and that alloys of iron and nickel are produced in the process of welding—it being a fact well-known to chemists and metallurgists that iron, with but even a small proportion of nickel, resists tho action of acids much more effectively than the pure metal. . THE STEAM CYLINDER. A good deal of recent discussion brings out prominently once more how little the wisest really know about tho behaviour of steam in tho cylinder of a steam engine. Just now the discussion as to the utility of the steam jacket is in the front, and the conflicting testimony, and opinions are anything but. reassuring. The unprejudiced engineer is likely to conclude, from all this discussion, that there are cases where the steam jacket represents economy ; also that there are cases where it brings about the reverse. But just what brings about this difference no one is wise enough to tell. What is needed is further knowledge of the

law.governing the condensation of steam in the cylinder of a steam engine; how it is affected by different conditions, etc. Then from this as a standpoint, figures can be made to apply to steam jacketing. Until a good deal more is learned about condensation of steam, the doctors will disagree as to the value of any means tending to prevent it. THE MICROPHONE FOR EARTH-TREMORS. The utility of the microphone for observation of earth-tremors and noises was soon recognised, and in Italy especially attention has been given to adapting the instrument for this use. We learn from the Rivista Scientifico-Industriale that Signor Baratca, finding some defects in a method of mechanical registration of the motions of a seismomicrophone, which he had devised, has substituted a photographic system with advantage. The device is briefly this :— The telephone wire is connected with a subterranean microphone. Before the tele-phone-diaphragm (vertical), and connected with its centre by a fine aluminium wire, is a short slip of the same metal, fixed below, and having a curved piece at the top, which rests against a small mirror, movable about a horizontal axis. This mirror reflects the light from a lamp and lens to photographic paper on a rotated drum. The light is momentarily shut off every quarter of an hour by a shutter arrangement worked electro-magnetically by the clockwork which moves the drum.

IMPROVEMENTS IN STEAM HAMMERS. ! In Chemnitz, the great tool-making centre of Germany, there have been made some improvemerfPs in steam hammers that are worthy of notice and in keeping with the tendencies of other steam machinery of our day. The hammers have two cylinders and two piston heads of different area, that operate on the principle of a differential engine; the steam, acting first in the same cylinder to raise the hammer, is then exhausted into the large cylinder, to make the down or working stroke. Heretofore steam hammers have been wasteful machines, the steam being used without expansion and the " clearance " in short strokes being lost. The differential plan seem? a good one, if there are also arrangements to use initial steam both above and below the pistons when required.—lndustry. AN ANTI-FRICTION SCREW NUT. An anti-friotion screw nut has been invented in which the bearing pressure falls on steel balls rolling in grooves in the nut and the threads of the screw. In the case of vertical screws, the balls " circulate" by falling from the top to the bottom of the nut and make regular " trips." Considering the abrasive wear in case of much pressure, find the complication, we think these may safely be set against the friction in a well-made square thread nut .of the common kind. Ball bearings are a questionable expedient in any case, so are roller bearings of all kinds, where there is any considerable pressure, and any complete obliteration of the whole system would be no loss in the mechannic arts, except for grindstones.— Industry. A NEW GAS METER. A new gas meter, known as the " March Thorp," is being made in considerable numbers in Manchester, England. By its aid a pennyworth of gas can be obtained by the consumer. The penny is dropped into a slot and pushed home by a piston or pusher, after which it drops into a locked drawer or receptacle. While the penny is being pushed through it releases a star-wheel which is operated by fingors or pawls fixed upon the drum. At the same time a conical valve, by which the admission of gas is controlled, is raised to a certain height. The revolution of this drum moves this valve down at a speed proportionate to that of the passing gas, and by the time the quantity which can be sold for a penny is delivered the valve closes, shutting off the supply. As soon as the gas is supplied the meter drum is again locked by the detention of the star wheel. If, while a pennyworth* of gas is being consumed, the pusher is raised to repeat the action without a coin, no additional supply can be got, and the introduction of another penny ensures the valve being opened as much further as is necessary to supply that value of gas, although the remainder of the first portion remains to be delivered.