H.—34.

PHYSICAL TESTING LABORATORY. Director: Dr. E. R. Cooper. The Physical Testing Laboratory was established during the year as a new Division of the Department with the object of bringing together in one organization the Department's staff and facilities for physical research and testing. The functions of the Laboratory are briefly as follows :— (1) To undertake physical research for the Department of Scientific and Industrial Research and for other Government Departments as required. (2) To undertake miscellaneous physical tests for various Government Departments. (3) To undertake physical tests necessary for the formulation and application of industrial standards. (4) To form a nucleus for a National Standards Laboratory in New Zealand to maintain primary reference standards of measurement. (5) To design, construct, and repair instruments for physical, geophysical, and chemical investigations within the Department of Scientific and Industrial Research. The Laboratory, with which is included an instrument workshop, has begun its work at 54 Molesworth Street. The nucleus of the staff had previously been working, under very cramped conditions, at the Dominion Observatory, where it was concerned with the maintenance of observatory equipment; a considerable amount of physical research and testing was also carried out. At the new premises in Molesworth Street there is a large workshop and two rooms which serve as laboratories. The workshop is equipped with lathes, drill, and milling-machine so that precision-instrument work can be performed, but at present in no great quantity. It should be pointed out that it is not the function of the Laboratory to construct instruments in bulk, but only to carry out the initial experimentation necessary to produce a model instrument which could then be copied if desired. (1) Present Facilities. The facilities at present available at the Laboratory include equipment for the following purposes :— General Physics.—Calibration of volumetric apparatus ; measurement of small intervals of time ; measurement of small dimensional changes —e.g., strain in structural members to 10 ~ 6 in., the shrinkage of concrete ; measurement of mechanical vibrations in buildings; measurement of air movement; determination of elastic constants of metals ; the testing of cloth, &c. Heat. —Temperature measurement to 750° C., shortly to be extended to 1,400° C. ; calibration of thermometers from —80° to 400° C. by direct comparison with sub-standards covering this range ; thermostatic control and humidity control; thermal insulation measurements on building-materials, including refrigerator insulants, range to be extended shortly to 0° C. and at mean temperatures up to 1,600° F. Apparatus will shortly be available for the determination of the temperature expansion coefficents of metals and refractories. Light.—Photometric equipment and sub-standard lamps for measurement of candle-power and lumen output by bench photometer (equipped with Lummer-Brodhun contrast photometer cube) and photometric integrator respectively; portable photometer for rapid measurement of illumination in situ; photoelectric cells for light measurements covering range from infra red to ultra-violet; calibration of ultra-violet lamps. Electricity. —General electrical measurements; calibration of D.C. and A.G. ammeters and voltmeters by direct reference to standard resistances and Weston cell; standard resistances with temperature control covering range 0-02 ohm to 100 ohms; calibration of wattmeters; measurement of magnetic properties of materials; determination of radioactive indicators. Special electrical measurements can be undertaken if required. (2) Summarized Report on the Year's Activities. (a) Examination of Possible Substitutes for Cork for Insulation Purposes. The following table shows the thermal conductivities of various materials : — Thermal Conductivities of Pumice, Flax, and Cell Concrete in B.T.U/Square Feet/Inch/ O F./Hour.

Tlie conductivity of cork is about U-3 in tiie above units. The thermal conductivity of pumice concrete, which consists of pumice fragments bonded together into a concrete, can be reduced by 20 per cent, by efficient drying. The moisture-absorbing properties of these materials have also been investigated.

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Mean Undried. Dried. Temperature of Specimen. Pumice (loose) particle size not exceeding \ in. .. .. 1-3 .. 8° C. fin. .. 1-4 i in. ..1-5 .. „ „ | in. .. 1-5 .. „ Pumice (loose) particle size between J in. and J in. .. .. 1-1 .. „ fin. and | in. .. .. 1-2 .. ,, „ | in. and in. .. .. 1-2 . . „ ,, J in. and | in. .. .. .. 1*0 ,, Pumice concrete particle size between J in. and J in. .. 2-3 .. 45° C. „ | in. and | in. .. 2-0 .. „ „ J in. and in. .. 2-5 2-0 „ Flax waste packed at optimum density 5 lb./cu. ft. .. .. .. 0-5 ,, Cell concrete of density 18-9 lb./cu. ft. .. .. .. ..