SUMMARY

  1. Aeroplane Reconnaissance and Photography. Expedition and economy in making surveys of areas little known or difficult of access by means of the aeroplane are stressed both in the papers and the subsequent discussion of this important modern development. Lieut. Salt indicates the nature and extent of the work which still requires to be done in topographical mapping alone and puts, forward the plea of urgency. He gives a full and critical account of the apparatus required and the methods employed, discussing these matters as surveyor and geographer. The other papers deal with similar problems from the point of view of the field geologist, and it would appear that whereas the topographical surveyor prefers vertical photographs from fairly high altitudes for the preparation of his maps, the observing geologist may require obliques at lower elevations. The advantages of aeroplane reconnaissance for observational purposes alone and not for the purpose of taking photographic records are made clear both in the papers and the subsequent discussion. Dr. Woolnough has developed a special technique in aeroplane observation for geological purposes by a study of shadows thrown by outstanding objects. Diagrams illustrating the method employed and a table for calculations based on shadows are included in his paper. In Dr. Woolnough's second paper the geological results achieved in the course of extensive flights made in Australia are recorded. The enormous area covered and the geological data recorded from areas in which little or no geology had been previously done fittingly illustrate the. importance of this new method of attack.

  2. The Aneroid Barometer in Reconnaissance Work. Dr. Sutton Bowman has developed a rapid and fairly accurate method of field surveying both for topographical and geological purposes in more or less mountainous country in which the aneroid barometer is the most important instrument used. The method is described in detail, while sources of error and methods of correction are discussed. He shows that the method can be used with advantage in tropical and sub-tropical countries where conditions are favourable. Judging from the discussion which ensued it would appear that this method cannot be used universally in the tropics. Mr. Evans pointed out that in Assam the diurnal variation curve is not sufficiently constant from day to day. This also was the Chairman's experience in Papua, where, in addition, the barometer was, at certain seasons, subject to violent fluctuations over short periods of time.

  3. The Evaluation of Surface Evidences of Petroleum.

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