NATURE 



[September 2, 1920 



ciently active form, and that even a good cement 

 may be considerably improved by the addition of 

 a suitable pozzolanic substance. White Portland 

 cement made from raw materials exceptionally 

 free from iron is not mentioned, but its manu- 

 facture is of some interest, and has been con- 

 ducted with success on a technical scale. 



The account of the consumption of energy in 

 grinding is not quite correct. It is not true of 

 most minerals that the energy required to separate 

 crystals along their cleavages is very small, and 

 clinker, although it may be in a state of internal 

 strain, nevertheless possesses a degree of hardness 

 which requires great energy to disintegrate it, as 

 may be shown by applying direct pressure to 

 single granules of clinker in a testing machine. 

 There are several suggestive notes regarding pos- 

 sible improvements in the manufacturing pro- 

 cesses. The author has long argued that the 

 logical goal of improved manufacture should be 

 the production of such a high temperature as will 

 yield a fused product, in which case a higher 

 percentage of lime could be used and a homogene- 

 ous cement obtained. Certain improvements in 

 regard to fuel economy and to the recovery of 

 potash are also suggested. 



On the subjects of chemical analysis and me- 

 chanical testing the author speaks with authority, 

 and the chapters dealing with these sections may 

 safely be used as a laboratory guide, whilst their 

 usefulness is enhanced by the inclusion of a 

 number of the more important official specifica- 

 tions for Portland cement in force in various 

 countries. The fact is mentioned that " a cement 

 which will pass the British standard specification 

 is at least as good as that acceptable under any 

 of the foreign specifications." 



The vexed question of the chemistry of Portland 

 cement is well treated, but a good deal of space 

 is occupied by an account of researches and specu- 

 lations which have no more than an historical 

 interest. It is not so widely known as it should 

 be that the whole chemistry of silicates has been 

 revolutionised by the brilliant work emanating 

 from the Geophysical Laboratory at Washington, 

 which has replaced guesswork by an accurate 

 physico-chemical survey of the systems concerned. 

 The triangular equilibrium diagram of the lime- 

 silica-alumina system is now known with sufficient 

 accuracy to serve as a practical guide in the 

 cement laboratory. The study of setting, on the 

 other hand, has not advanced very greatly beyond 

 the stage reached by Le Chatelier. The author, 

 in referring to the work of Stern, has overlooked 

 the fact that the examination of clinker and 

 cement by reflected light after etching has been 

 used successfully by several workers, and that 

 NO. 2653, VOL. 106] 



excellent photographs of the fine eutectic struc- 

 tures have been published, some of them in Japan. 

 These points might well receive attention in a 

 future edition, and would still further increase 

 the value of a very useful book. 



C. H. Desch. 



Psychology, Normal and Subnormal. 

 (i) Psychology of the Normal and the Subnormal. 

 By Dr. H. H. Goddard. Pp. xxiv-t-34g. 

 (London : Kegan Paul, Trench, Trubner, and 

 Co., Ltd., 1919.) Price 255. net. 



(2) Psychology and the Day's ]Vork: A Study in 

 the Application of Psychology to Daily Life. 

 By Prof. E. J. Swift. Pp. ix -1- 388. (London : 

 George .Vllen and L'nwin, Ltd., 1918.) Price 

 10s. 6d. net. 



(3) The Child's Unconscious Mind: The Relations 

 of Psychoanalysis to Education: A Book for 

 Teachers and Parents. By Dr. Wilfrid Lav. 

 Pp. vii -f 329. (London : Kegan Paul, Trench, 

 Trubner, and Co., Ltd., 1919.) Price ids. net. 



UN'TIL the last half-century psychology was 

 based almost exclusively upon the observa- 

 tion of a highlv intelligent and highly civilised type 

 of mind — usually the mind of the psychologist 

 himself. Modern psychology owes its remarkable 

 progress chiefly to two factors : first, to the addi- 

 tion of the method of experiment to the method 

 of observation ; and secondly — a factor the import- 

 ance of which is less generallv recognised — to 

 the extension of these two methods to the study 

 of simpler types of minds — of the minds of 

 animals, of children, of savages, and of abnormal 

 adults. The recent increase in the number of in- 

 stitutions for feeble-minded children has now pro- 

 vided psychology with the simplest human material 

 available for investigation. Just as the ultra-rapid 

 camera slows down the kinematographic picture of 

 the swift movements of leaping and running, so 

 Nature, by an arrest of the brain, retards the 

 normal development of the child so. that it can 

 be observed and tested at leisure. 



(i) The laboratory attached to the \'ineland 

 School for Feeble-minded Children — a laboratory 

 unique of its kind, not only in .America, but also 

 in the world — has been utilised for such studies 

 since 1906. Dr. Goddard 's book provides a 

 popular resume of the conclusions progressively 

 accumulated by the investigators in that labora- 

 tory. It is not a psychology merely of the men- 

 tally defective child. It is a psychology of the 

 normal human mind as illuminated and illustrated 

 by the observations upon the mentally defective. 

 The volume, hoviever, is by no means confined to 

 observations carried out at \'ineland. Indeed, 



