Science Siftings

New Zealand Tablet, Volume XLIII, Issue 18, 4 May 1916, Page 45

Science Siftings

By ‘Volt.’

Discovering Earthquakes.

„ Though the man in the street might" easily mistake a slight seismic disturbance for the rumbling of a traction engine ,or an explosion, the marvellously delicate instruments which record earthquake shocks are immune from such deceptions. - Sunk in the earth on solid foundations/ the recording pen of the > seismometer ignores any local tremblings which have not a seismic origin; but the faintest real earth quakings, though they have travelled thousands of miles through the earth, set the pen tracing the tell-tale graph by _ means of which the seismologist calculates the place, time, and magnitude of the happening. Years before the genius of the Japanese gave birth to the science of seismology, a very rough record of a Scotch earthquake was obtained at Comrie by means of a basin of treacle. The basin was about half-full of treacle, and by noting the magnitude and direction of the treacle marks made on the inside when the ‘ quake ’ disturbed its normal level, a fair approximation was obtained as to the magnitude and movement of the seismic waves which caused the earth disturbance. " ' ;

A Surgical Magnet.

A strong magnet for lifting weights is not an unusual engineering operation, but it is not customary to enlist a surgical one for the purpose. ? This ;is being done by one of the most powerful magnets in the world/ and has been installed by the Westinghouse and Electric Manufacturing Company in the relief department of. its East Pittsburg works. The magnet is mounted on a box containing the resister, which is used to • regulate the amount of current flowing through the coils. It requires 4000 watts for its operation, or enough power to supply one hundred lamps of thirty-two candle-power each, and is designed for operation on seventy volts. It is not an infrequent occurrence for steel and iron workers to get bits of metal in their eyes or hands. Previous to the installation of a magnet the only means of removal was by probing, a method which is as uncertain as it is painful. Since this machine was put in operation, it is a very simple proceeding to extract such particles. The portion of the body in which the foreign . particle is embedded is placed near the pole, tip of the magnet, the switch is closed, and the magnet does the rest. . .Some- remarkably small pieces have been extracted in this way. . The pole, piece is removable, a number of different shapes being supplied for various classes of work. ’ /

Measuring Starlight. / rf There are only two ways of learning anything about the stars one of them is to measure J their movements, and the other to examine their light. This phrase occurred in the introduction of a lecture given by Dr. F. W. Dyson (Astronomer Royal) at the Royal Institution, London, on measuring the brightness of the stars. He explained that there were other methods of examining starlight besides measuring its brightness, but he wanted to confine his remarks to the single property that had been greatly investigated of late and had led to important, results. Measuring the luminosity of a star is a very different problem from that of measuring the candlepower of a lamp or an electric light, because of its wonderful minuteness. The lecturer gave an idea of the difficulty, by saying that there were somewhere between one and two hundred million stars within’ telescopic vision of the earth,, and yet all the light that the world received from the stars was about onehundredth part of that received from {.he full moon, or, measured in more definite terms, the light given out by a 16-candlepower lamp when viewed at a distance of 47 yards. The standard by which one could measure these small lights was perforce an exceedingly small one, and many had been proposed, of which the most successful before the introduction of photography —had been made ■by reflecting moonlight so as. to form an artificial star, with which others could be compared. . - Nowadays, the effect of the light on a photographic plate led to very important results. / Amongst others, the inspection _of the photographs had shown us how the stars thin out in various directions through space, the fainter and _ more distant stars being exceedingly numerous jn - the direction of the milky way, but comparatively few in other directions. This seemed to show that our solar system was very/.nearly, in the middle of the stellar universe, "and that the-stars; so far as we could observe them, were spread out in an. oval of .which the long diameter was eight and a half times as long as the short>one.; .