SCIENCE SIFTINGS

New Zealand Tablet, 9 September 1920, Page 46

SCIENCE SIFTINGS

(By “Volt.”)

Heating Rooms by Power. In a lecture recently delivered before the Institution of Civil Engineers in London, England, Sir Du* gald Clerk revived an interesting proposal made by the late Lord Kelvin for the heating of rooms. This proposal is not easy to explain without diving into mathematics and the abstruse laws of heat, but it may be expressed as a process of using an engine to extract some of the heat from the cold air outside a room, and adding it to the heat of the air inside the room. The curious and puzzling thing about this process *S that the heat so added is, under certain conditions, much greater than the heat equivalent of the work done by the engine. In theory, therefore, an electric motor may be used very efficiently to warm a room. Whether the notion will work out satisfactorily in practice remains to be seen, but in view of the everincreasing cost of fuel this fascinating problem is likely to be soon attacked by British engineers. Reading by Sound. A remarkable electrical invention has recently been made by means of which the blind are enabled to read by sound. The invention is an application of the well-known principle whereby the resistance of a selenium electric cell can be varied by alterations in the intensity of the light impinging upon the plates. , In this particular application variations in the light are produced by reflection from the printed pages of a book over which the apparatus is passed. Every different printed letter will 'cause a slight alteration in the reflected light, and these variations in the light will, by varying the resistance of the selenium cell, induce corresponding fluctuations in the current of electricity generated by the cell. By connecting the cell to what is in effect a telephone receiver, the blind man is enabled to recognise each individual letter by the sound produced as the instrument passes over the successive lines of print. Measuring Tunnels.

Although all our great railway companies use the same rail gauge, their tunnels are all different in height, width, and shape of arch (says Tit Bits, London). During the war there were many queer loads to be carried to the coast, and this matter of tunnels came into prominence. Tanks, it was found, could not be carried on the ordinary trucks through the tunnels of one of our southern railways. There was not sufficient room. The result was that special trucks had to be built, the beds of which were only nine inches above the rail. There is now in existence a special car, built expressly for measuring tunnels. There is nothing very

new about this, for in the past, when any company contemplated building a new type of engine, an existing engine was taken and fitted with projections or metal fingers coinciding with the dimensions of the new engine. This was run over the line to ascertain whether it would pass the tunnels all right. The new car is an ingenious arrangement which does all this automatically. It measures at the same time the width and the height of bridges and tunnels. It also measures all curves, and by means of a pendulum suspended inside the car shows exactly how much higher one rail is than the other. Of the crew of two, one man takes the readings of the various instruments while the other jots them down.