Dec. 26, 1889] 



NATURE 



171 



the vicinity of London, although, as the operations of 

 the builder are extended in every direction year by year, 

 their number gradually, but surely, diminishes. Where 

 Dr. Greene writes from his own experience, he is always 

 worth listening to, but he has a faith in Morris, which, as 

 might be expected, often leads him awry. He quotes 

 from the Bible about the "Sparrow" on the house-top 

 (p. 13), but the bird alluded to is the Blue Rock Thrush 

 {Monticola cyanea), for which cf. Canon Tristram's " Fauna 

 and Flora of Palestine" (p. 31). The illustration on 

 p. 23 is not that of the 'common Sparrow, but of the 

 Tree-sparrow. At p. 46 he gives a tabular list of charac- 

 ters by which to distinguish the Missel-thrush from the 

 Song-thrush, in which the former bird is said to have 

 " no song to speak of." Evidently, Dr. Greene has never 

 heard a " Storm-cock " in full swing. He does not love 

 the Greenfinch, but this need not lead him to say that 

 the species likewise "has no song." Acock Greenfinch, 

 perched on the top of a tree in the nesting season, and 

 singing to his mate sitting on the nest below, has a 

 charming and varied song, like that of a very powerful 

 Canary. The Whitethroat, of which Dr. Greene appears 

 to know only one species, is placed in the sub-family 

 MotacillidcB, and it will surprise many ornithologists to 

 hear that the song of the Chiff-chaff is continued even 

 till late in September (this information is derived from the 

 Rev. F. O. Morris !). The Blackcap does not winter in 

 Eastern Africa, and it can hardly be said that the Siskin 

 '' rarely nests in this country." We mention these points 

 at the risk of appearing hypercritical, but we recognize 

 in Dr. Greene an author who has the knack of writing 

 good natural history books for the young, and it is there- 

 fore the more incumbent upon him to be scrupulously ac- 

 curate. Let him discard Morris, and stick to Seebohm's 

 " History of British Birds," or to the new edition of 

 <' Yarrell." Some pretty illustrations by Mr. Whymper 

 form an additional attraction to his little book. 



R. BOWDLER SHARPE. 



DESCARTES. 



History of Modern Philosophy. " Descartes and his 



School." By Prof. Kuno Fisher. Translated by J. P. 



Gordy, Ph.D., and edited by Noah Porter, D.D., LL.D. 



(London : T. Fisher Unwin, 1887.) 

 /\ MONG the many histories of modern philosophy 

 '^ few are so interesting and attractive as that by 

 Prof. Kuno Fisher. The present volume consists of a 

 translation of the third revised German edition, which 

 includes the period of Descartes and his school ; and the 

 admirable way in which the author deals with so difficult 

 a subject and his boldness in overcoming it are worthy 

 of the highest praise. 



The book is divided into three parts, the first of which 

 is preceded by an introduction to the subject, showing the 

 course of development of the Greek philosophy and that 

 of the Middle Ages, with an account of the early history 

 of Christianity and the Church, concluding with the 

 periods of the Renaissance and the Reformation. 



In Part L we have an account of the early history of 

 Descartes. He was born in the year 1596, a few days 

 before the death of his mother, and was a weak and sickly 

 child. Throughout his childhood he showed a strong 



desire for knowledge, and it was on this account that 

 his father called him his " little philosopher." 



Descartes was among the first pupils in the new school 

 that was started at the Royal palace at La Fl&che by 

 Henry IV. ; at the age of seventeen he was committed 

 to the care and tutorage of Father Dinet. During his 

 school life he was among the chosen pupils who, on June 

 10, 1 6 10, solemnly received the heart of the king, which, 

 by Henry's will, was to be buried in the church of La 

 Fl^che. 



While going through a two years' course on philosophy, 

 he became completely fascinated by mathematics, and was 

 thereby incited to make a further study of it ; and later 

 on in hfe, seeing the true spirit of mathematics as a 

 method of solving problems, he began by algebraical 

 equations to solve geometrical problems, and thus to 

 him is due the discovery of analytical geometry. On 

 the completion of his school career, the state of his 

 mind may be gathered from his own words—" ... I 

 found myself involved in so many doubts and errors, 

 that I derived no other result from my desire of learning 

 than that I had more and more discovered my own 

 ignorance." 



The next few years of his life were spent in military 

 service in Holland and Germany, after which, at the age 

 of five-and-twenty, he travelled for nine years ; to him 

 his travels were studies in the great book of life, and 

 during them he " did nothing but wander now here, now 

 there, since I wished to be a spectator rather than an 

 actor in the dramas of the world." The last period of 

 his life consisted of the development and publication of 

 his works, and the founding of a school of philosophy, 

 concluding with his illness and death during his stay in 

 Stockholm, to which place he was invited by Christina, 

 then Queen of Sweden, who, being deeply interested in 

 his works, found the difficulties in his system could better 

 be explained by Descartes himself than by anyone else. 



Although the philosophy of Descartes treats of the 

 whole realm of Nature, we will here touch only upon 

 those parts that are interesting to us from the scientific 

 point of view. Not by any means the least important is 

 his attempt to explain the origin of the world by purely 

 mechanical laws. He bases his theory on the rest and 

 motion of solid and liquid bodies, and the influence of 

 the latter upon the former. Before entering upon this 

 hypothesis, the mechanical principle of his explanation 

 of Nature is first brought before us. He treats motion 

 as a mode of extension, and explains it as the " transla- 

 tion of place (transport) of one part of matter or of one 

 body from the vicinity of those bodies which directly 

 touch it, and are considered at rest, into the vicinity of 

 others." 



The causes of motion are next dealt with, showing us 

 that all changes are due to outward collision, and that 

 since space is by no means empty, but is full of bodies 

 moving in every direction, we may get a great number of 

 coHisions, the various possible results of which he then 

 goes on to discuss. According to his principles, then, 

 bodies are quite destitute of force, excepting that of 

 resistance ; changes in the material world are due to 

 external collisions, and motion, therefore, is due to 

 impacts. Comparing the views of Descartes with those 

 of GaUleo and Newton, we cannot do better than quote 



