October 12, 1911] 



NATURE 



477 



realisation of a plan, as the finalist view would have 

 it. A plan is given in advance, but evolution is a 

 creation unceasingly renewed, a development of an 

 original impetus in various directions. Two of these 

 directions are represented by the world of plants with 

 their fixity and insensibility, and the world of animals 

 with their mobility and awakened consciousness. 



" But the waking could be effected in two different 

 ways. Life, that is to say, consciousness launched into 

 matter, fixed its attention either on its own movement 

 or on the matter it was passing through ; and it has 

 thus been turned either in the direction of intuition or 

 in that of intellect." 



Intuition could not go very far, and shrank into 

 instinct. Intelligence became more and more free, 

 and " it can turn inwards on itself, and awaken the 

 potentialities of intuition which still slumber within 

 it." While Bergson shows very finely how the plant 

 may sometimes rouse itself from its torpor and the 

 animal sink into vegetativeness, how instinct may be 

 mingled with intelligence, and intelligence penetrated 

 by instinct, yet his definite conclusion is that the 

 differences between vegetative torpor, instinct, and 

 intelligence are differences of kind. 



"The cardinal error which, from Aristotle onwards, 

 has vitiated most of the philosophies of nature, is to 

 see in vegetative, instinctive and rational life, three 

 successive degrees of the development of one and the 

 same tendency, whereas they arc three divergent direc- 

 tions of an activity that has split up as it grew." 



And it is from this that the author passes to his 

 even more important conclusion that while intelligence 

 guides us into matter and delivers to us the secret of 

 physical operations, it is instinct — which is sympathy — 

 that will give us the key to vital operations. 



" Intelligence goes all round life, taking from out- 

 side the greatest possible number of views of it, draw- 

 ing it into itself instead of entering into it. But it is 

 to the very inwardness of life that intuition leads us — 

 by intuition I mean instinct that has become dis- 

 interested, self-conscious, capable of reflecting upon its 

 object and of enlarging it indefinitely." 



Thus while nature-poetry is in no sense biology, it 

 may be a verv important complement. 



J. A. T. 



TIDES AND ORBITS. 

 Scientific Papers. By Sir George Howard Darwin, 

 K.C.B., F.R.S. Vol. iv., Periodic Orbits and Mis- 

 cellaneous Papers. Pp. xviii + 592. (Cambridge: 

 University Press, 1911.) Price 15s. net. 



IN this fourth volume Sir George Darwin has for 

 the present completed the task of editing his 

 papers, a task whicli he commenced four vears ago 

 on the invitation of the syndics of the Cambridge 

 University Press. If we may judge from the fact that 

 nine papers in the present volume have appeared since 

 the publication of the work was started there is reason 

 to hope that a supplementary volume will be needed 

 before many years are past. That volume when it 

 comes will have to contain, if it is to be consistent 

 with former volumes, pioneer investigations of a high 

 order in some difficult branch of applied mathematics. 

 To one who desires to speculate along what line Sir 

 George Darwin's future work is likely to take him 

 NO. 2l8g, VOL. 87] 



the present volume is of especial interest. For in the 

 papers classed under the head "Miscellaneous Papers 

 in Chronological Order " will be found several early 

 papers containing the germ of much of the later more 

 important work. Several of these papers (notably 

 11, 12, 13) would appear to be by-products of larger 

 investigations which were already (we judge 

 from the chronological list of papers) well in 

 hand when these investigations were published. 

 But the paper " On the perturbation of a comet in the 

 neighbourhood of a planet," which was followed after 

 an interval of four years by the historic investigations 

 on periodic orbits, does look like the first attempt along 

 a new and fruitful line of investigation. In fact, 

 though differing in scope and nature from the larger 

 work, the small paper to which we have just referred 

 might quite fairly, from a historic point of view, have 

 been placed in the section containing the periodic orbits 

 papers, as a preliminary piece of research. This sec- 

 tion is the most important part of the volume under 

 review, and we must discuss it in some detail. 



In the introduction to the well-known memoir in 

 the Acta Mathematica, the author speaks of the pro- 

 digious amount of numerical work involved in his 

 attack on the problem of periodic orbits. He adds : — 



" It is not for me to say whether the enormous labour 

 I have undertaken was justifiable in the first instance ; 

 but I may remark that I have been led on, by the 

 interest of my results, step by step, to investigate 

 more, and again more cases. Now that so much has 

 been attained I cannot but think that the conclusions 

 will prove of interest both to astronomers and mathe- 

 maticians." 



Recent successful applications to problems of celes- 

 tial astronomy of what are to a large extent Sir 

 George Darwin's methods would alone justify his 

 heavv work. But quite apart from these applications 

 the paper has great intrinsic value. The important 

 stability discussion and the useful account of the 

 method of mechanical quadratures practically 

 developed by the author both serve a very useful pur- 

 pose to the student. The presence of a paper by Mr. 

 S. S. Hough, his Majesty's astronomer at the Cape, is 

 a valuable addition to the section. It not only serves 

 to bridge over the gap between Darwin's first and 

 third papers and to supply an important addition to 

 the theory of the subject, but it also supplies an 

 account of the orbit work from a different point of 

 view from that of the author. It may not unfairly be 

 compared to Schwarzschild's account of Poincare's 

 work on revolving bodies, and its presence alongside 

 Darwin's papers is of great value. It should be added 

 that the illustrations have been well reproduced, and 

 that from an interesting appendix some idea may be 

 gleaned of the heavy computing work involved in 

 these researches. Here it seems not unreasonable to 

 refer to Sir George Darwin's generous and thoughtful 

 appreciation of his great co-worker's investigations 

 in his own field. His address on presenting the gold 

 medal of the Royal Astronomical Society to M. Poin- 

 care is full of interest. This, with his two British 

 Association addresses, will form the chief item of 

 interest in this volume to the non-mathematical reader. 

 We can only glance at two points of interest here. 



