92 



NA TURE 



[July 15, 1922 



Annual Visitation of the National Physical Laboratory. 



A LARGE number of visitors were present at the 

 -**■ National Physical Laboratory on the occasion 

 of the Annual Visitation on June 27. The guests 

 were received by Sir Charles Sherrington, president 

 of the Royal Society and chairman of the General 

 Board ; and Sir Joseph Petavel, Director of the 

 Laboratory. As is usual on such occasions, the 

 various departments were thrown open and an 

 interesting series of exhibits was arranged, illustrative 

 of the work carried on in the institution. 



In the Department of Aerodynamics, exhibits 

 were shown in most of the six wind tunnels. In 

 the largest of these, which has a cross section of 

 14 ft. x 7 ft., an aerofoil model was set up showing 

 the methods of measuring the lift and drag. The 

 section of the aerofoil under test was on a scale 

 approximately one-fifth of full size. In another 

 channel were shown additions made to the standard 

 type of balance, whereby for one setting of the model 

 the component forces and moments in three directions 

 can be determined. This represents a considerable 

 saving of time in the process of testing. The dis- 

 continuous flow of air past a barrier was demonstrated 

 in an effective manner by means of smoke released 

 into the stream of air before it reached the obstacle. 

 Other exhibits included an aeroplane model showing 

 the method of obtaining the distribution of pressure 

 over the wing, an apparatus used for determining the 

 thrust and torque of model propellers, and an in- 

 genious wind direction finder. 



The additions to the Engineering Department, 

 consisting of a large experimental shop and a set of 

 offices, have been completed during the year and have 

 much relieved the congestion. Among the exhibits 

 were two machines for testing the efficiency of spur 

 gears and chain drives. In both of these machines 

 the regenerative principle is made use of, so that the 

 power consumption is only that absorbed by the 

 element under test. Thus, to determine the losses 

 corresponding to an actual transmission of 100 h.p.,. 

 a power of the order of 5 h.p. suffices. The efficiencies 

 can be measured to an accuracy of 01 per cent. A 

 new machine for testing reinforced concrete slabs and 

 columns was also shown. The slab specimens can 

 be tested in sizes up to 16 ft. x6 ft. and 14 inches in 

 thickness, and the columns from 8 to 20 feet in 

 length ; the maximum load is 60 tons. It was 

 interesting to note that it was found possible to 

 support the columns by means of knife-edge pivots. 

 During the year, a plant has been completed for the 

 production of asphalt road carpets. This enables 

 the constituents to be mixed accurately in the 

 proper proportions, prior to laving and testing in the 

 standard road-testing machine. Other exhibits in 

 this department included apparatus designed for 

 the measurement of the temperature and pressure 

 of the oil film in lubricated journals, the investigation 

 of heat losses through pipe covers, the determination 

 of the fatigue ranges of stress in materials by the 

 strain method, and for the investigation of the 

 detonation of a mixture of air and liquid fuels in 

 closed vessels. 



In the Metallurgical Department, a much-needed 

 extension of space has been provided during the year 

 by the addition of an extra floor on the Wernher 

 building. Considerable attention has been devoted in 

 this Department during recent years to the study of 

 aluminium and its alloys, and examples were shown 

 of an alloy developed at the Laboratory which 

 is specially suitable for aeroplane engines. " Pistons 

 and piston rings of this material were on view. A 

 specimen of aluminium was exhibited which had been 



NO. 2750. VOL. I io] 



submitted many times to an alternate treatment of 

 rolling and melting without any effect on its tensile 

 strength. A very effective experiment was shown on 

 specimens of an aluminium-zinc alloy, which were 

 heated in a furnace at a temperature of 370 C. and 

 then quenched bv immersion in water. Within a 

 period of five minutes, a considerable generation of 

 heat occurred — due to the breakdown of an unstable 

 solid phase — which rendered the specimen almost too 

 hot to be held in the hand. An interesting series 

 of micro-photographs, taken during this period, 

 showed the structural changes occurring, which 

 are accompanied by great variation in hardness. 



In the section of the department dealing with 

 refractory materials, a new recuperative gas furnace, 

 working under natural draught, and intended for glass 

 melting, was running, while in the section of aero- 

 nautical chemistry the viscosity method for character- 

 ising deterioration of fabrics was demonstrated. 

 Other exhibits in the Metallurgical Department were 

 a high temperature thermostat arranged for obtaining 

 very slow rates of cooling, and an ingenious relay 

 for controlling furnace currents. 



In the Heat Division of the Physics Department, 

 various methods for the -measurement of thermal 

 conductivity were demonstrated. These included a 

 new apparatus for dealing with thin sheets of material 

 and for studying the effects of pressure on the thermal 

 conductivity, a large scale apparatus for experiments 

 on insulators for cold storage purposes, and a similar 

 apparatus which has been used for measuring the 

 conductivity of a series of building materials. A 

 method for investigating the convection of heat in 

 transformer oils was shown and also a device for the 

 automatic operation of a ventilating valve with small 

 changes of temperature of the air inside and outside 

 a room. Various types of hygrometers were also 

 exhibited. 



In the Thermometry Division a new type of 

 resistance bridge was shown with dials reading to 

 o-ooi° C, with a platinum thermometer of 10 ohms 

 fundamental interval. 



In the Radiology Division apparatus designed for 

 the X-ray spectroscopic investigation of structure 

 of materials, the measurement of radium salts, the 

 standardising of barium platino-cyanide pastilles, the 

 investigation of protective values of X-ray materials, 

 and the X - ray examination of metals were ex- 

 hibited. 



In the Optics Division, various types of apparatus 

 for measurement and specification of colour were 

 shown. These included a Nutting monochromatic 

 colorimeter, a Lovibond tintometer, a Bawtree 

 colorimeter, and a trichromatic colorimeter for 

 standardisation purposes designed and constructed 

 at the Laboratory. In the latter instrument the 

 mixing of the three primary colours is accomplished 

 by rotating a periscopic prism which passes rapidly 

 in front of three sectorial openings of variable angles 

 in which the coloured filters are placed. Among the 

 exhibits in this division was also a differential refracto- 

 meter for liquids having nearly the same refractive 

 index, while a new immersion method for measuring 

 the internal bore of a glass tube was also demonstrated. 



The Metrology Department (Glass Testing Section) 

 showed a new equipment designed for the accurate 

 calibration of hydrometers against a hydrostatic 

 balance. The liquid in which the hydrometer is 

 immersed is surrounded by a water bath controlled 

 by a thermostat. The whole of this apparatus, can 

 be moved under a special balance from the scale pans of 

 which are suspended two plummets of the same mass 



