Vibration and Pervibration in Concrete Depositing

The CHAIRMAY (Dr. Oscar Faber, O.B.E., M.Inst.C.E., Vice-president), who regarded the paper as one of the most interesting ever presented to the Institution, proposed a hearty vote of thanks to the author for the extraordinarily interesting collection of photographs he had shown, as well as for the paper itself, and for the admirable way in which he had presented it.

The rapid growth of aerial transportation during the last ten years so admirably illustrated by the activities of Imperial Airways Ltd., and particularly the wide interest shown in the spectacular flight of Scott and Black from Mildenhall Aerodrome to Melbourne in two and a half days, have focussed public attention on the urgent necessity for providing adequate landing fields and aerodromes in this country. It is noteworthy that H.R.H. The Prince of Wales remarked at the recent Airport Conference, “Take care of the wheels and the wings will take care of themselves.” The aeronautical engineer has indeed done his share, and such enormous strides have been made in aircraft design that the operational speed of machines is approaching 200 m.p.h. If, therefore, it is true that “time is money,” here is economy with a vengeance. H.E. Brooke-Bradley

Revolutionary changes in structural design are so rare that particular interest attaches to occasional reports, principally from foreign countries, describing the manufacture in light aluminium alloys of structures which would normally be of steel. Clearly the choice of material is not dictated by some irresponsible whim, but by economic considerations, or other equally strong justification. For many years, the use of aluminium alloys has been standard practice for certain special types of structures, e.g., aircraft, and if proof were necessary of the suitability of aluminium alloys for withstanding stress, fatigue, corrosion, and other factors looked for in a structural material, it would be found in the behaviour of the delicate, complicated girderwork of a rigid airship, or the less intricate but equally elegant structure forming the fuselage and wings of an aeroplane. For such structures, however, the paramount importance of the stress-weight ratio reduces to a secondary consideration those questions of comparative cost which in general engineering are so important. The fact that the cost of duralumin may be 2s. 6d. per lb., whereas structural steel costs less than 2d., is of less importance than the fact that l-lb. of duralumin in the form of a bar of any given length will support nearly three times the load carried by l-lb. of structural steel of the same length. E.T. Painton