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treated and untreated. These were measured for linear dimensions and moisture content after subjection to each of several known atmospheric conditions (30 per cent. R. 11., 50 per cent. R.H., and 85 per cent. R.H.) and the " movement " of corresponding treated and untreated samples compared. (11) Recorder for Phosphate-works to register simultaneously Weight and Density of Charges of Acid and Rock : Temperature of Acid- The initial general design of the above recorder has been supplied to the works concerned after preliminary experimentation. When approval or suggested modifications have been received by the Laboratory, the detailed design and any necessary developmental work will be continued. (12) Equipment for inspecting the Overhead Pantograph of an Electric Locomotive in motion along Rail Track. —The optical section of the physics laboratory developed equipment described above, from which a design was submitted to the Railways Department. Part of the construction of the prototype is being done by that Department, and the Laboratory will fit and align the optical system. (13) Linen Flax.—lnvestigations into the quality of New Zealand fibre led to attempts to improve both yield and quality by alterations to the retting process. New methods of determining the optimum retting end-point were found to give improved results, and these were then applied to full-scale trials. Only a slight improvement was obtained, although tests on a small scale continued to show improved yield and quality. Exhaustive tests were carried out to determine the reasons for this, which suggested that variable conditions throughout the retting-tanks made a true end-point determination very difficult. A subsequent attempt to determine a mean end-point by study of the gas-flow from the tanks was inconclusive. During these tests other experiments were carried out to observe the effect of different retting procedures ; samples of green flax were retted direct from the paddock ; various methods of drying the flax after retting were tried ; improved yields were obtained by careful handling to give improved cutting of the straw, the extent to which scutching was affected by humidifying dry straw was studied fully, and tests were carried out on a turbine scutcher in which a new system of crimping rollers was installed. A full report on these investigations was supplied to the Linen Flax Committee. (14) Meters for testing rapidly the Moisture Content of Wood and of such Materials as Seed, Soil, &c.—Electric moisture meters have been developed in the electrical laboratory. One is a capacity-operated device, based on a National Physical Laboratory design, and was made to measure the moisture content of wheat. Another was built for the Army Inspection Department for moisture measurements in Pinus radiata. An original circuit was developed which consisted of an electric resistance meter to measure the resistance between two test prods thrust into the timber. The indicating device is a 500 microamp meter and the instrument is calibrated in two ranges having a ratio of approximately 3 to I over a total range of approximately 0 per cent, to 30 per cent, moisture. (15) Steel-sorter for Rod and Bar Stock. —At the request of the Public Works Department Mechanical Branch a magnetic steel sorter was constructed, based on a design supplied by them. The device is mains operated, and a magic eye indicates similarity or differences in samples of steel under test. The instrument is sensitive to differences of chemical composition and of physical state, so that it can be used as a hardness comparator also. It is purely a comparator and a known reference sample is necessary. Other types of electric sorters are being investigated and developed. (16) Improved Circuit for D.P.L. Controlling Pyrometer. —Although no cases of failure had occurred in previous pyrostats, it was considered desirable to have a greater margin of safe operation with voltage variations and other variable conditions. As a result of considerable investigation a circuit was developed which would operate over a wide range of voltage, was independent of the variations in photo-cell characteristics, and was definitely more reliable under the most adverse conditions. The new circuit is simpler than previous circuits, and any previous pyrostat can be altered in a few minutes. (17) Measurement of Low Rates of Air-movement. —In connection with the observations on State houses mentioned above, it was found necessary to develop a method of recording estimates of wind velocities down to as low as 3 ft. per minute. A hot-wire anenometer has been designed and calibrated in a wind-tunnel to give repeatable results. (18) Standardization of Relative-humidity Measurements.—Experience has shown that there is great difficulty in obtaining agreement between results from the various standard methods of measuring relative humidity unless great attention is paid to the conditions under which the measurements are carried out. A constant-temperature bath has been designed to hold its temperature to better than x y C., and in this is inserted apparatus for measuring relative humidity of the dewpoint, the wet and dry thermometer, and the chemical (pressure) methods. Accuracy to \ per cent, is hoped for in all three methods when the experiments in hand have been completed. Repairs, Tests, and Calibrations.—Electrical meters (140), industrial thermometers (45), pyrometers (33), pressure gauges (70), barometers (17), telescopes (32), binoculars (58), rangefinders (7), theodolites (6), sextants (12), chronometers (9), precision clocks (28), stop-watches (14), laboratory balances (9), sots of analytical weights (8), weighing-machines for Transport Department (14), foot candle meters (8), tachometers (6), precision surveyors' levels (6), hydrometers (6), camera lenses (5), butyrometers (23). Tests were made on the following materials and equipment and statements of examination issued : flame-proofing of aircraft electrical motors ; railway-track recorder ; fluorescent lamps ; tungsten lamps; fibrous cement wallboard and other types of wallboard ; corrosion Mazak bomb-tails ; chromalloy wire, shipment of; hot-water bottles ; canvas water-bags ; toothbrushes ; fading of paint; asbestos roofing-sheets ; pumice concrete ; rubber air-hose ; catgut; salvus valves for fire hydrants ; noise level of aircraft propellers. Metkology Labobatory The manufacture of munitions and other war requirements in New Zealand during 1944 -45 has called for large numbers of gauges. Seventeen thousand gauges were certified in all ; nine thousand of these were of a uniform simple type. The laboratory now undertakes the checking and sealing of

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