MEASURED IN MILLIONTHS!

Evening Star, Issue 19666, 20 September 1927, Page 8

MEASURED IN MILLIONTHS!

WHERE NATION'S STANDARDS ARE PRESERVED AY bon you pay for a yard ol cloth, an ounce of tobacco, a unit of electricity, or a pint of milk, yon are unwittingly recording a. vote ol confidence in the work ol a team ol hairsplitting scientists at tlio National Physical Laboratory, Tcddington. For this institute, set on the border ol Bnshcy Park, and less than a mile from Hampton Court Palace, has as one of its chief objects the preservation ol existing standards of weight, mass, length, and volume, and the determination of now ones as occasion demands. Together with a similar establishment at Berlin, and the Bureau of Standards at Washington, the Teddinglon Laboratory leads the scientific world in matters of nice calculation demanding accuracy lo the nth! GIFT OF QUEEN VICTORIA. The laboratory has little history, save in its scientific achievements, in i'JUU Queen Victoria gave Bnshey House, lor years the residence ol William IN ~ to tho Royal Society, and it was in this building, still a part of the laboratory, (bat tho “ X.P.L.” was first housed. Beginning with Ibis one building and (ewer than thirty scientists, the laboratory has rapidly attained its present imposing spread of fifty acres with some ten large buildings and a stall' of (..or live linmired. There are seven principal departments—namely, physics, electricity, metrology, engineering. metallurgy, aerodynamics, and the William Fronde national tank. To visit them is Lo explore strange territory of the mind where a hair's breadth is regarded as a tremendous thickness ami a t-peck of sand a colossal, load! 00,000 TESTS A MONTH. Whenever supreme accuracy is required in any part of a- manulactnred product, samples are submitted to the laboratory for testing purposes. Thus, every month, the heat division of the physics department tests between 50,000 ami 00,000 thermometers supplied by manufacturers. The same division"is concerned with measurement of temperatures up to B,oUUdcg C,! Problems ol cold storage are also studied here. The radiology division Ims charge ol the British Radium Standard, and measures the radium content ol samples submitted. All questions relating lo the application ol X-ray analysis to industrial problems are now being studied, and especially keen just now is the search for an improved form of protective clothing lor X-ray operators. One room ol the sound division js particularly striking, it is used to determine the sound-absorbing qualities ol any material. Double walls and triple doors exclude noises Irout without, while several thicknesses of dull brown felt on the walls, ceiling, and floor, giving the room a queer, cave-like appearance, absorb interior echoes. in the centre of a large concave reflector a microphone is supported which emits a sound wave that travels tlio length of the room. The sound energy transmitted is accurately measured. Next the material to be tested is fitted across tho centre of the room so that all sound reaching the instrument must pass through it, a similar sound transmitted, and a second reading taken tv Inch, on comparison with the first, will show the sound-proof value of the muteriai. THE LEGAL ELECTRICAL STANDARDS. Tho electricity department contains an ampere balance, a, voltmeter standard, and an instrument for determining the standard ohm; these are the property of tho Board of Trade, and represant tho legal electrical standards ol the Empire. Comparisons of electrical standards in this department are made with an accuracy of one part in a million! In tlio wavemeter room wireless frequencies and wave lengths are measured to an accuracy of 1/10(!,lX)l)! . , Ol immense interest is tlio wont ot tlio wireless division. At present the scientists aro investigating the properties of the “ heavisidc layer,” a mysterious and totally unforsecn _ lament of wireless transmission. How is ft, the plain man asks, that a v*irelc.s.s t\a\o which, we are told, travels in a straight lino can be sent from London and picked up in Australia, with the huge bump of the earth's surface in between? Logically, the wave should

leave the earth’s surface directly the latter begins to curve away. This would probably he the case wore it not lor the “ beaviside layer.” a, thick hand of ionised air between Si.l and Pin kilos high, which relied.v the naves hack' to earth again. Thus a Birmingham listener to a Paris station receives two waves, one parallel to the ground and another reflected by (lie “ heavisidc layer.” A more distant listener would receive, only the reflected wave. SERVICE FOR WIRELESS USERS. This .same division also performs a useful sendee for wireless list oners throughout the country in the shape of hi-munthly (first and third Tuesdays) transmissions of a series of stundard waves by which amateurs and others can check their installations. 'These waves are measured before transmission to an aeenraev ol more than 1/50,0001 in tiio metrology division there is a standard clock kept in a constant temperature chamber, by which nil manner of timekeepers are regulated. Ordinary clocks and watches sent from manufacturers, ' ships’ chronometers, and deck watches are, daily compared with the standard timepiece by means of readings on a plotting chronograph. Here, too, are line instruments for measuring mass to six decimal places of a gramme! There is a gramme balance, a miracle of nice workmanship, which weighs minute bodies with an error of only one in a million! The readings are taken by means of optical levers at (he farther end of the room in order to prevent the heat from the. body affecting the extreme sensitiveness of the balance. In a long narrow corridor stands a fifty-metre tape bench for testing the length of .surveyors' lines to on accuracy'' of l/200tli part of an inch! At present the Metrology Division is examining a problem that may mean the disuse of the present standard yard anil metre, the metal rods in London and Paris, by which all length measurements are governed. Tt lias long been recognised that these metal standards vary in length not only with changes of temperature, but also as the result of a natural “creep” of the metal itself over the space of many years. The department has recently perfected an apparatus whereby a standard wavelength of light may be substituted that would not be subject to those changes.

t The Photometry Division is at present concerned with the illumination of rooms, factories, picture galleries, and public hails- by daylight and artificial light, and problems of design lor shipj railway, and signal lights. Here also are maintained the standards of illumination of the country by which the candle-powers of all sources of light arc calculated.

A similar example is to be louud iu the road testing machine, a device consisting of a central shaft from which radiate eight metal arms with wheels at the extremity of each. The eight wheels follow each other round-about fashion—cm a narrow circular track which can be laid -with any kind of prepared road surface. The contractor desirous of testing the strength of his “ carpet,” a.s the road covering is called, lays it on the circular track as lie would on an ordinary road. Various tests are apidicd for thickness and levclncss, and then for seven hours a day for many days the eight wheels rotate on the prepared “ road,” which is kept continuously under water to create the severest possible conditions for the test. At the end of the trial, the strip of circular road will have borne—or failed to bear?—the equivalent of 400,000 tons per square yard!

EXPERIMENTS WITH MODEL SHIPS. Finally, there is tho William, Eroudo National 'Tank, the gift of Sir Alfred Yarrow, for experiments and - research in ship design. It is of necessity Riven an entire building la itself. More Ilian live times the length of a public swimming liaih. the tank lias a capacity for t .'iod.OUO gallons of water. When experiments are to be made on any vessel, drawings are sent to the laboratory, where an cx'aet model, usually to the scale of 1—25, is executed in paraffin waxi The model is (hen towed the length of the tank at a uniform speed’ by an oleotricalWarriago astride the tank, fitted with a dynamometer and oilier instruments to record the changing resistances of the water at various speeds. The tank, which is IHi I t deep in tho middle, has a false bottom which can be raised when it is desired to observe the effects of a model in shallow water; and another ingenious device enables tho operators to create small or large waves and all the marine effects of stormy weather. A series of tests of this kind, including (ho making of the model, can usually be completed within a week, a, considerable feat. It is only necessary to talk to munno engineers (o learn of the _ immense value of the data gleamed in recent years by the lank experiments, and it is generally acknowledged that if tho laboratorv had nothing else to its credit the work of the William Fronde tank would assure it a permanent place in the world of experimental science.— ‘John o' London's Weekly.’