November ii, 1920] 



NATURE 



337 



ling-, a motor hurries along the road, the clouds 

 are drifting. All is change and motion. It seems 

 that all history is change, and all is hurrying by 

 us as we stand. But is it not a truer view, 

 tertainly a less egoistic one, to see history as one 

 eternal whole, and ourselves as voyagers through 

 it, our vision of it ever changing? All our experi- 

 ments, our measurings and comparisons are them- 

 selves part of the great web ; we ourselves are part 

 and parcel of it, and must acknowledge our in- 

 capacity to put ourselves outside. \\\ our pictures 

 and conceptions of the universe in time and space 

 are but pictures, and the painters are many. There 

 are strange differences between their records of 

 what they have perceived — more, indeed, of differ- 

 ence than of similarity. We go to a picture- 

 gallery ; there is so much of difference that at first 

 there seems little in common. Yet gradually we 

 become conscious that the pictures are all drawn 

 from a common life. We begin to be able to 

 analyse the painters, and see what kind of a mind 

 is looking out upon it, to detect a point of view. 

 In so doing we grow more dear as to the one 

 reality behind all the pictures. 



This is a true parable of the great change that 

 has been consummated in physical thought by 

 Einstein's work. It is the rect^nition of the rela- 

 tivity of our space-and-time pictures that has 

 clarified our understanding of the universal phe- 

 nomena. Gravitation has not been explained. The 

 mystery of it is ten times greater than before. To 

 Newton it was one among many properties of that 

 fundamental mystery "matter." It is almost true 

 now to reverse the order and say that matter is 

 inc of the manifestations of the fundamental 

 iivstery of gravitation. 



The reader of Einstein's exposition will need 

 to ponder hard if he is to get to the heart of the 

 matter. For it is a spiritual adventure upon which 

 he has to embark. The very clarity and simplicity 

 of the book may hide this from the over-confident. 

 Ihe parable may be understood and its meaning 

 lost. But to those who have the vision the world 

 of physics will take on a new and wonderful life. 

 Ihc commonest phenomena become organic parts 

 of the great plan. The rationality of the universe 

 becomes an exciting romance, not a cold dogma. 

 The thrill of a comprehensive understanding runs 

 through us, and yet we find ourselves on the shores 

 of the unknown. For this new doctrine, after all, 

 is but a touchstone of truth. We must submit all 

 our theories to the test of it ; we must allow our 

 deepest thoughts to be gauged by it. The meta- 

 physician and he who speculatrs nvrr thr mraning 

 of life cannot be indifferent. 

 NO. 2663, VOL. 106] 



The Cambridge British Flora. 



The Cambridge British Flora. By Prof. C. E. 

 Moss, assisted by specialists in certain genera. 

 Illustrated from drawings by E. W. Hunnybun. 

 Vol. iii. Portulacaceae to Fumariaceae. Text : 

 Pp. xvi-l-300. Plates: Pp. vi+191. (Cam- 

 bridge: At the University Press, 1920.) Price, 

 two parts, 6/. 15s. net; two parts in one volume, 

 7/. net. 



THE previous volume of "The Cambridge 

 British Flora" was reviewed in Nature of 

 August 6, 1914. Since this review was written 

 many things have happened. Dr. Moss has been 

 appointed professor of botany at the University 

 College, Johannesburg, and has been unable to 

 give personal attention to the volume during its 

 passage through the press. The syndics of the 

 University Press acknowledge valuable assistance 

 given by Mr. A. J. Wilmott, of the botanical 

 department of the British Museum, in correcting 

 proofs and in dealing with questions which are 

 normally settled by an editor. In July, 1918, Mr. 

 E. W. Hunnybun died. A sympathetic note by 

 Mr. Wilmott, at the beginning of the present 

 volume, gives an interesting account of his method 

 of work in preparing the illustrations, which makes 

 clear both its advantages and limitations. The 

 character of the illustrations has been much dis- 

 cussed among British botanists, but it became 

 evident that Mr. Hunnybun could work only on his 

 own lines, the accurate delineation of an individual 

 specimen, and was also unable to supply the 

 botanical details of structure of flower and fruit 

 which, in the opinion of many, would have 

 enhanced the value of the illustrations. .\s 

 permanence is a consideration in a work of such 

 importance as a standard British Flora, it is 

 surprising to find the plates printed on a chalk- 

 faced paper. Other events have tended to delay 

 the appearance of the present volume, and to cause 

 the serious increase in cost of production, which 

 has necessitated raising the price to nearly three 

 times that of the previous volume. The syndics of 

 the Cambridge University Press must view this 

 addition to their difficulties with grave anxiety, 

 and it is to be feared that many students of our 

 British flora who would wish to possess the book 

 will be unable to meet the increased cost. The 

 critical elaboration of a number of families will be 

 of considerable value should the work fail of 

 completion; but British botani.sts will feel deeply 

 disappointed if it cannot be carried through 

 satisfactorily. 



The families included in vol. iii. are Portul- 



