Reviews — Fossil Remains of Man. 129 



sinks into the ground, saturation being realized after some weeks* 

 copious springs then burst forth everywhere, permitting the removal 

 of soluble products ; this must be the time when the zone of leaching 

 grows at the base and the phenomena of depart or leaching are 

 completed near the surface. At the end of the rainy season this 

 flow gradually ceases, the ground dries, the solutions become 

 concentrated, and are drawn up by capillarity into the upper zone ; 

 there the dissolved products are deposited little by little, the water 

 finally evaporating at the sun-heated surface, where the precipitation 

 and concretion of the hydrogels is completed. 



The conditions of lateritization given above fit satisfactorily the 

 mineralogical and chemical data given in Professor Lacroix' memoir ; 

 but it is not evident that the description of the happenings in the 

 rainy season is based on personal observation, for the author's visit 

 coincided with the winter. 



VI. The Age of Laterltes. 



Professor Lacroix finally states his views on the age of various 

 sorts of laterite, regarding it as probable that all the phenomena 

 considered in his memoir are still in a state of active evolution, 

 although no direct observation of this can be made, except in the case 

 of ferruginous concretionary action at the surface of the cuirass. But 

 he gives evidence to show that the process of lateritization must 

 be a slow one. There are laterites of at least two ages, as proved 

 by the eroded cliffs of ' fossil laterite ' contrasted with the laterite 

 A' alluvions of the valleys, these two types corresponding in position 

 to our Indian high-level laterite and low-level laterite. He finally 

 concludes that (p. 351) — 



' ' Le debut de la laterisation en Guinee est fort ancien et date peut-etre de 

 plusieurs periodes geologiques, sans qu'il possible de songer a aucune precision 

 en l'absence de toute formation sedimentaire datee." 



In conclusion, it is perhaps permissible to regret that this admirable 

 piece of work should contain several numerical mistakes in connexion 

 with the analyses, and that the author has not seen fit to illustrate 

 his memoir with at least a sketch-map of the localities mentioned, nor 

 to separate clearly the conclusions firmly founded on observations 

 such as the sequence of mineralogical changes characterizing lateriti- 

 zation from those based less securely on probability rather than on 

 observation, such as the conclusions brought forward in Section V 

 of this paper. 



:e.:E]"v:E:E"ws- 



I. — A Guide to the Fossil Remains of Man in the Department of 

 Geology and Paleontology in the British Museum (Natural 

 History), Cromwell Road, London, S.W. With 4 plates and 

 12 text-figures. 



DURING the last two years the lively controversies concerning the 

 significance and interpretation of the skull-fragments found by 

 Mr. Charles Dawson near Piltdown have bewildered and confused the 



DECADE VI. — VOL. II. — NO. III. 9 



