264 REPORTS ON THE STATE OP SCIENCE, ETC. 



Stresses in Overstrained Materials. — Report of Committee (Sir Henry 

 Fowler, Chairman ; Mr. J. G. Docherty, Secretary ; Prof. G. Cook, 

 Prof. B. P. Haigh, Mr. J. S. Wilson). 



The following interim report is submitted. 



The programme of work set out in the report for 1929 has been commenced. 



An investigation of the stress-strain relation up to and beyond the yield point 

 is being carried out in the Engineering Laboratory of the Royal Naval College, 

 Greenwich, by Mr. J. G. Docherty and Mr. F. W. Thome, but the tests are not 

 yet complete. It is hoped to publish the results soon. 



Professor G. Cook, in the Engineering Department, King's College, London, is 

 investigating [a) the efiect of non-uniform stress produced by torsion, flexure, and 

 internal pressure, on the initial yield point in mild steel, (b) the stress diistribution in 

 the initial stages of plastic strain for these cases. It is hoped that the results of these 

 experiments will be published in the autumn. 



It is hoped that a full report of these experiments, and also the other papers 

 proposed in the 1929 Report, will be presented along with the report for 1931. 



The Committee ask to be reappointed for another year. 



£arth Pressures. — Fifth Interim Report of Committee (Mr. F. E. 

 Wentworth-Shields, Chairman ; Dr. J. S. Owens, Secretary ; 

 Prof. A. Baer, Prof. G. Cook, Mr. T. E. N. Fargher, Prof. A. R. 

 Fulton, Prof. F. C. Lea, Prof. R. V. Southwell, Dr. R. E. 

 Stradling, Dr. W. N. Thomas, Mr. E. G. Walker, Mr. J. S. Wilson). 



Since its last report the Earth Pressures Committee has met once, viz., on May 29, 

 1930, at the Building Research Station at Garston, Watford, by the kind invitation 

 of Dr. Stradling, to see the research work which is being carried out there by Prof. 

 C. F. Jenkin, whose report is attached, and who explained to the Committee the 

 nature of the research and the apparatus he was using. Those present were impressed 

 with the fact that the investigation of the actual pressure and resistance of clay is 

 very much more complex than previous investigations have led us to suppose, and 

 indeed that the same maj' be said about sand. Professor Jenkin is on his guard 

 against the many factors, which may lead to quite wrong conclusions in this kind of 

 research, and although the results of any research cannot be foretold, it seems likely 

 that his work will lead to information and practical results. The Committee recom- 

 mend that his and their work be carried on for a further period. 



Progress Report on Earth Pressure Experiments. 



Since my last report my apparatus has all been moved to the Building Research 

 Station, Watford. Considerable delay has occurred in building my new laboratory, 

 but it is now complete and I have started working in it. 



In August last I visited the large research laboratory, Berlin, known as 

 Versuchsanstalt fiir Wasser und Schififsbau (Testing Station for Water and Ship- 

 building). This estabUshment is carrying out regular tests of soils encountered in 

 connection with the new dock works at Bremerhaven. The soil samples are packed 

 in air-tight cases to ensure against loss of moisture on the joiu-ney. Briefly, the 

 following tests are carried out : 



The moisture content is determined by drying. 



The grain size is determined by sieving, and in the case of finer grains, by water 

 separation. 



The specific gravity is determined by removing the air with carbon tetra- 

 chloride, and then measuring the volume with water. 



The proportion of carbonate of lime is determined by measuring the CO 

 given off when the grains are treated with sulphuric acid. 



The nature of the grains is determined by microscopic examination. 

 The acidity is determined by measuring with an electric bridge, giving the 

 hydrogen-ion content. 



