SOME NEW SCIENCE MARVELS

Hokitika Guardian, 21 April 1921, Page 1

SOME NEW SCIENCE MARVELS

(By H. G. Field in Daily Mail)

Not the least wonderful among tho many marvellous inventions of the last half-century are tho machines and instruments that have been devised for the detection and measurement of minute quantities, whether it be of heat, electricity, or matter, and that now form an essential part in the outfit of any laboratory of importance. It is now possible, by means of refined galvanometers, to measure electric currents of one-thousand-millionth of the strength of those used in an ordinary electric bell circuit. To such an instrument the tiny current produced in one’s little finger when that member is bent is easily detectable,

Some of the most sensitive instruments are those employed to measure the'amount of heat or light radiated by a body at a distance. The radio-micro-meter, for instance, which depends upon the production of a very small electric current when any radiation falls upon it, has been used to measure the heat and light radiation received on the earth from the moon and from Jupiter, and is so sensitive that it will respond if anyone in its neighbourhood should blush.

Again, scientists now have two methods of chemical analysis at their command which enable them to detect the minutest traces of any particular element in a substance.

The first of these is the spectroscopic method. Most elements when vapourised at a high temperature and examined by means of the spectroscope indicate their presence by producing cliaracterictic coloured lines instead of the ordinary spectrum; for example, sodium, produces two bright yellow lines where the yellow part of the spectrum would ordinarily come. The least paiticle of any element in the vapour that is being examined is sufficient to produce its own characteristic lines, and it is possible to demonstrate by this means the presence of a one-hundredth-niilliontili part of an ounce of sodium in

the substance under examination. Still more delicate is the positive ray apparatus of Sir J. J- Thomson, in which each element is made to record its presence, so to speak, by means of a curved line on a photographic plate, the position of the line depending on the density of the element. This instrument will show the presence ol helium in a thimbleful of air. YVhen it is stated that helium exists in the air in the minute proportion of one part in one hundred thousand parts of air. some idea of the wonderful sensitiveness of this machine can be gained. The measurement of small distances has not been brought to the same wonderful exactitude as have most other measurements, but instruments aie in daily use in most laboratories that will measure to within onc-five-thousandth

of an inch. Of all forms of measurement, however, weighing is tho one that has reached the highest degree of accuracy. An instrument that deserves especial mention is tho micro-balance designed l,v Ramsay and Gray and used by them to weigh and estimate the density ol the rare gas niton, which escapes slowly from radium and of which the% possessed only one-twenty-tliousandtli of a cubic inch. They were able to effect both these measurements accurately by means of this balance, which will weigh to within a one-thousand-millionth part of an ounce.