October 29, 1914] 



NATURE 



223 



cyst is always present in the skeletal muscles of 

 affected sheep in large numbers, the more 

 advanced the disease the larger being- the numbers 

 present; (2) the itching can be reproduced in 

 rabbits by infection with sarcosporidial emulsions. 

 It would be more satisfactory to have the com- 

 plete demonstration with sheep instead of with 

 rabbits; but no doubt this will come. In the 

 meantime Dr. M'Gowan has to admit that he 

 has no treatment to suggest, but recommends 

 that the affected animals should be sent to the 

 butcher before their case has become too serious, 

 whilst the ewe stock should be kept up from the 

 progeny of animals older than two years. In- 

 breeding also should be conducted with great 

 caution. 



(3) The study of the formation of the soil owes 

 much to the Russian investigators Dokutschajeff, 

 Kostytscheff, Sibirceff, Glinka, and others, and 

 in this volume we have a very convenient sum- 

 mary of what they have done, and a good descrip- 

 tion of Russian soils by one of the best of the 

 modern Russian workers. One of the troubles 

 of the past has been the lack of a widely-accepted 

 system of classification ; several have been pro- 

 posed, but none has been universally adopted. It 

 is largely to the Russian investigations that we 

 owe the possibility of a definite system ; their 

 insistence on the necessity for more adequate 

 recognition of climatic factors has widened our 

 views on the subject and enabled better groupings 

 to be made. More survey work has still to be 

 done before a final classification can be set up, 

 but in the meantime the scheme outlined in the 

 present book is of distinct value. 



The author recognises two great g-roups of 

 factors in soil formation : internal factors — such 

 as the composition of the rock — and external 

 factors, such as climate. He accordingly sets up 

 two great classes of soils : endodynamomorphic, 

 in the formation of which the internal factors 

 have predominated, so that the properties of the 

 soil are governed by the properties of the origina- 

 ting material ; and ectodynamomorphic, where the 

 external factors predominated, the influence of 

 weathering and transporting agents, the climate 

 to which the soil Eas been exposed, etc., having 

 outweighed the effect of the composition of the 

 original material in determining its properties. 

 j Examples of the first are the various black soils 

 I containing calcium carbonate, which he calls 

 rendzina soils. These include our fen soils, the 

 , black earths (tschernosem, etc.). The ecto- 

 I dynamomorphic soils are subdivided into six 

 ; groups according to the amount of washing they 

 ' have received during the process of formation- 

 The tropical " laterite " soils come at one end of 

 I NO. 2348, VOL. 94] 



this chain and the alkali soils at the other. There 

 are, of course, transition forms, but in the main 

 the world's soils fall fairly easily into the scheme. 

 The book will be read with much interest by aU 

 students of the soil. E, J. R. 



THE EVOLUTION OF PHILOSOPHICAL 

 THOUGHT. 



Greek Philosophy. Part i, Thales to Plato. By 

 John Burnet. Pp. x -f 360. (London : Mac- 

 millan and Co., Ltd., 1914.) Price 105. net. 



THIS is the second volume of a series by 

 various writers entitled "The Schools of 

 Philosophy," and edited by Sir Henry Jones, pro- 

 fessor of moral philosophy in the University of 

 Glasgow. The author states in the preface that 

 his chief aim has been to assist students who wish 

 to acquire a first-hand knowledge of what Plato 

 actually did say in the dialogues of his maturity. 

 He should be eminently fitted for this task, as he 

 ■ was Taylorian scholar in 1885, and ever since he 

 has kept himself immersed in Greek literature. 



In a footnote on the last page he states that 

 he has edited the whole text of Plato, and the 

 usual books of reference give a list of his other 

 works, which are all connected with the Greek 

 classics. This footnote, however, like a woman's 

 postcript, contains the key to his mind, as it 

 begins by saying that he was drifting into a 

 "hopeless scepticism," from which apparently he 

 now believes himself convalescent. Yet he be- 

 gins the introduction with the paradoxical words : 

 " No one will ever succeed in writing a history of 

 philosophy." The catalogue of the British 

 Museum provides one horn of the dilemma, and 

 his latest book supplies the other. It deals with 

 philosophers, or with some of the greatest and 

 earliest, but it contains no information likely to 

 assist the rising generation of undergraduates and 

 philosophers in ascertaining what were the ideas 

 these ancients were groping after. Only by a 

 supreme effort of the maieutic art could a student 

 ascertain from the book itself that in physics one 

 of their greatest stumbling blocks was the equa- 

 tion of motion of a falling raindrop, 7/=^~^Vh) 

 which they only had under observation when v 

 was equal to H. 



The discussion of this problem is noticed by 

 Duhem in his article, p. 272, "Roger Bacon et 

 I'horreur du vide," in the commemoration volume 

 of Roger Bacon essays just published. The word 

 " natural " attached to motion always presupposes 

 a gravitational cause. The horror of the void 

 arises from the metaphysical notions derived from 

 Aristotle now embedded in scholastic or neo- 



