222 



NATURE 



[February i6, 1922 



Building Materials and Heat Insulators. 



HTHE Department of Scientific and Industrial Re- 

 ■*■ search has issued two special reports qn floors 

 and thin walls, the result of work undertaken by an ad, 

 hoc Building Materials Research Committee appointed 

 to investigate new materials and constructional 

 methods in connection with housing schemes ^H.M. 

 Stationery Office, is. 3d. net and 6d. net respectively). 

 Some eight types of floors were dealt with, comprising 

 hollow tiles, brick and tile, reinforced concrete, ash 

 concrete, and ordinary wood joists. Suitable sections 

 or units of these floors were erected and tested for 

 carrying capacity to destruction. The results are sum- 

 marised in tabular form, showing the weight of the 

 floor, load carried, deflection, breaking load, age on 

 testing, elastic limit, and so on. These results are 

 also plotted diagrammatically, and drawings are given 

 showing the construction of each floor to scale. The 

 ash concrete proved weak, and the ordinary joisted 

 floor, though possessing obvious disadvantages from 

 some aspects, appeared to hold its own in the matter 

 of strength. The experiments on thin walls included 

 the testing of brick and concrete blocks and slabs and 

 coke-breeze materials. Consistent results showed that 

 the crushing strength of the walls varied from 67 to 

 83 per cent, of that of cubes of the materials respec- 

 tively employed. Lengths of wall of 14 in. and 3 ft. 6 in. 

 and 2f in. to 4^ in, thick were dealt with. These 

 strips were 8 ft, 6 in. high, and the horizontal pull 

 necessary to make the wider strips collapse was 

 measured. The materials built in lime mortar on 

 account of early failure under test give rise to criticism 

 of lime as a binding agent, but surely the behaviour 

 of walls so built after only twentv-four days cannot be 

 fairly compared with that of similar walls built in 

 cement which sets in a day or two. Lime was used 

 in all our national buildings until comparatively recent 

 years ; it is cheaper in actual cost and labour than 

 cement, and its wider use merits revival. These 

 experiments are valuable and interesting ; it has to be 



remembered, however, that the country builder usually 

 fears new methods, and is apt to put unduly high prices 

 on unknown forms of construction. 



The fifth special report of the Food Investigation 

 Board, issued by the Department of Scientific and 

 Industrial Research, consists of an account of experi- 

 ments on heat insulators suitable for use in cold 

 stores. The work has been carried out at the National 

 Physical Laboratory by Dr. Ezer Grifiiths, and so far 

 has been devoted to the determination of the thermal 

 conductivity of a number of materials adapted to low- 

 temperature insulation. In the experiments a warm 

 surface, consisting of a metal plate electrically heated, 

 was maintained at a steady temperature and placed 

 opposite to a similar plate cooled by brine circulation, 

 the material under test filling the space between the 

 two plates. Special precautions were taken to 

 eliminate errors arising from edge effects in the warm 

 plate and air convection in the material, and when a 

 steady temperature had been attained in both plates 

 the heat passing through the lagging was deduced by 

 measuring the watts furnished to the warm plate. 

 The results obtained show that the conductivity in 

 C.G.S. units for slab cork is ooooii ; granulated cork, 

 ooooii to 000019; slag wool, 0-000102; and dry char- 

 coal, 0000122. A number of other substances giving 

 higher values were also tested, and mention is made 

 of a cellular form of rubber which from preliminary 

 tests appears to be superior to any other material 

 examined, its conductivity being about 0000085. As 

 an appendix to the report, a description is given of 

 the apparatus devised by Dr. Griffiths for determining 

 the specific heats of the materials under notice. 

 Although other factors, such as moisture absorption 

 and liability to organic growths, have to be taken 

 into account in choosing a lagging for a cold store, 

 the figures obtained by Dr. Griffiths should prove of 

 much practical value to those engaged in the re- 

 frigerating industry. 



Industrial Fatigue. 



T^HE Industrial Fatigue Research Board, which 

 -'■ has recently been reconstructed as an advisory 

 body under the Medical Resea'-ch Council, is to be 

 congratulated upon the publication of two highly 

 valuable and most interesting reports. These are 

 doubtless a legacy to it from the older Board the 

 wider sphere and greater liberty of action of which 

 were recently brought to an end by the Treasury under 

 the pretext of economy. They are published by H.M. 

 Stationery Office at is. and 25. respectively, Report 

 No. 12 being on vocational guidance and Report 

 No. 15 on motion study in metal polishing. The 

 former of these reports, written by Mr. B. Muscio 

 (who has since accepted a professorship in the Uni- 

 versity of Sydney), gives a detailed review of the 

 literature on vocational selection. The list of nearly 

 sixty books and papers at the end of the report indi- 

 cates the diligence which the author has brought to 

 bear on his task. The report is divided into three 

 sections : (i) introductory, (2) summary of special 

 investigations, and (3) future investigations. The 

 second section, filling forty-two of the fifty-seven 

 pages, contains a most able and critical account of 

 the psychological tests that have been applied to 

 clerical, engineering, and metallurgical occupations, 

 music, printing, salesmanship, telegraphy, telephone 

 NO. 2729, VOL. 109] 



exchange work, transport work, war experiments, etc. 

 Prof. Muscio indicates in his last section the wide 

 field which is now open for future investigations con- 

 ducted on a broader scale and on a more systematic 

 basis than hitherto. 



Not less valuable is the Board's Report No. 15 on 

 motion study in metal polishing bv Messrs. E. Farmer 

 and R. S. Brooke. These investigators prove very con- 

 clusively what an enormous wastage of effort now 

 occurs in the "buffing" (spoon and fork polishing) 

 trade owing to the lack of a systematic course of 

 training for newly entering workers. They indicate 

 the principles on which such a course should be based, 

 and give data derived from the actual application of 

 those principles, which " prove conclusively that a 

 beginner, given adequate training, can become an 

 expert dollier within a very few days, but left to her- 

 self, without proper instruction, she probably will 

 never become highly skilled, and will continue all her 

 life to waste her energy in unnecessary and unpro- 

 ductive movements." The influence of fatigue was 

 ingeniouslv studied bv means of a recording watt- 

 meter which they applied to the machines employed 

 for removing scratches and other imperfections from 

 spoons and forks. It was found that as towards the 

 end of the day the girls' output diminished and their 



