February 23, 1922] 



NATURE 



233 



i 



Theorie der Parallellinien von Euklid bis' Gauss " 

 (Leipzig, 1905), a better translation, and better 

 nnotated, than his own. 

 To come to the translation : Prof. Halsted quotes 

 remark by " one of the foremost classical scholars 

 America " that the Latin of Saccheri is almost 

 classical and is remarkably clear. It is a pity that 

 it should not have been translated into equally 

 classical English. The translation is, in fact, the 

 reverse, and it is clear that the translator was not 

 well equipped for this part of his task. He seems 

 imperfectly acquainted with the force of " quin," 

 ice mistranslating it completely ; apparently he 

 s not know the meaning of " morem gerere," 

 ince he translates " ut morem gereret tot Magnis 

 iris . . ." by "as made a custom with so many 

 eat men . . . " ( ! ) ; he renders ' ' in rem suam ' ' 

 y "in his affair " instead of " for his purpose," 

 ' superetur ab " by " would exceed ' ' instead of 

 ' would be exceeded by," " liquet " by " it flows " 

 instead of "it is clear," " dico . . . manifestae 

 falsitatis redargui inimicam hypothesim " by "I 

 say I have disproved the hostile hypothesis by a 

 manifest falsity " instead of " I say I have con- 

 victed the hostile hypothesis of manifest falsity," 

 " ad tuendas reliquas Definitiones " by " regarding 

 other definitions " instead of " for the purpose of 

 maintaining other definitions." He is habitually 

 \ ague as to moods and tenses, commonly translating 

 I he subjunctive by the indicative, future by present, 

 etc. And what are we to say of such a sentence as 

 this : ' ' But here (^ice versa) in fact is permitted 

 the designation of however most small an acute 

 angle at the point A while still the sect AB to 

 which is to be erected the indefinite perpendicular 

 HX, may be taken of any length whatever "? The 

 mathematician must make of this what he can. For 

 our part, here and in many places, we find it a 

 relief and comfort to be able to turn for light to 

 the Latin on the opposite page. 



The Structure of East Africa. 



The Rift Valleys and Geology of East Africa. By 

 Prof. J. W. Gregory (with ten appendices by 

 various authors). Pp. 479 + 20 plates + 5 maps. 

 (London: Seeley, Service, and Co., Ltd., 1921.) 

 325. net. 



PROF. GREGORY is to be congratulated on 

 having found, or made, opportunity to com- 

 lete his work in East Africa, begun so brilliantly 

 nd adventurously in 1892-3. Returning to the 

 )untry for a short visit in 1919, under favourable 

 uspices and vastly improved conditions, he was 

 il>le to collect much new information in rapid 

 traverses, often by motor-car, where, as we are 

 NO. 2730, VOL. 109] 



now reminded, on his previous journey his researches 

 had been curtailed by the truculence of drunken 

 warriors, or by drought, scarcity of game and 

 ferocity of lions, or other such amenities of the eld 

 " safari " travel. Meanwhile there has been con- 

 siderable exploration of this and neighbouring 

 regions by other observers, and Prof. Gregory has 

 essayed in the volume before us to combine what 

 is known of the geology of East Africa into a 

 coherent whole. That he has performed the task 

 with courage and skill need scarcely be said ; every 

 scrap of information finds its appropriate place in 

 his scheme and helps to consolidate it, so that we 

 have a clear and logical account of the geological 

 history of the region throughout the ages. All the 

 rocks are classified into formations with local names 

 and placed in position in the geological scale. 



With the present meagreness of our knowledge of 

 these vast spaces, there may seem to be a premature 

 positiveness in the method of presentment, but the 

 author defines his attitude explicitly in his preface : 

 " Progress in East African geology requires a 

 scheme by which new facts may be classified. The 

 classification adopted is tentative and must be 

 amended as well as amplified. Pioneer geology has 

 to choose between the rashness of using imperfect 

 evidence or the sterility of uncorrected, unexplained • 

 facts." These sentences must be remembered by 

 the reader ; otherwise he may sometimes be startled 

 at the big leap, taken with a bold " therefore," from 

 the narrowness of the stated fact to the breadth 

 of the deduction. Used in accordance with 

 the author's suggestion, as an adjustable framework 

 to accommodate new information, the book will be 

 of particular service to every future worker in the 

 same field, while to the geologist at large it provides 

 the readiest means of gaining a general idea of the 

 eastern portion of the African continent. 



As implied by the title, Prof. Gregory's well- 

 known and much-discussed conception of ' ' the Great 

 Rift Valley " runs as a leading theme throughout, 

 and monopolises the shorter two of the four parts 

 into which his book is divided. This is, however, 

 largely a repetition, with some modification, of 

 matter already published, here conveniently reas- 

 sembled. It is parts 2 and 3, with the technical 

 appendices, that constitute the major and most 

 ser\ iceable portion of the work 



In part 2, consisting of twenty^two chapters, the 

 author describes the geology, mineral resources, etc., 

 of British East Africa (now Kenya Colony). This 

 part contains the details of the new observations 

 made by the author in his recent traverses ; hard 

 reading for anyone unacquainted with the ground, 

 but invaluable to the next investigators in exhibiting 

 the evidence on which the generalisations and classi- 



I 



