To an ever increasing extent, weighing instruments for the determination of masses of more than 50 kg are designed as high-accuracy weighing instruments of accuracy class II rather than as medium accuracy weighing instruments of accuracy class III. Consequently, the masses required for testing must meet higher accuracy requirements. The uncertainty of a 5 t mass scale set up at the Physikalisch-Technische Bundesanstalt (PTB) is assessed on the basis of an analysis of the uncertainties which can be attained. This mass scale allows masses of 10 kg, 50 kg, 500 kg and 5 t to be calibrated with relative uncertainties of 5 × 10-8, 6 × 10-8, 3 × 10-7 and 1,5 × 10-7. With their aid, deadweights of up to 50 kN for force standard machines can be determined with relative uncertainties of 4 × 10-7.

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The May 1, 1939, forecast of inflow to Lake Mead was as follows: Accumulated precipitation during the period October 1938–April 1939, inclusive, compared with similar accumulative records for corresponding periods of the two previous seasons, indicated that the total precipitation to May 1, 1939, was 90 per cent of the average of the previous years, and that the inflow to Lake Mead would probably be 8,000,000 acre‐feet between May 1 and August 1, 1939. Based on water‐content of snow, records of this character available since 1936 indicated that the water‐content as of May 1, 1939, was 91 per cent of the previous three‐year average, or that the probable inflow would be 7,000,000 acre‐feet.