so 



KNOWLEDGE. 



February, 1911. 



examples, and might therefore be used to supplement a course 

 of lectures ; but we do not think a student would find it an 

 easy introduction- to the subject. The author has not the 

 qualities of a good guide; he neither turns round to survey the 

 ground already covered, ncr .~t-'ps to point out the path by 

 which the chmb is to be coiiiinued. The different subjects 

 are not made complete in themselves, nor is the relative 

 importance of different theorems or methods suggested. For 

 instance, the Ellipsoid is introduced on page S3, but instead of 

 being treated with proper respect, the form of its surface is 

 dismissed with a reference to an example in small print on 

 page 9. The book is well printed, but we are disappomted at 

 the paucity of illustrations which, with geometrical methods, 

 might be used to reinforce the analytical reasoning which the 

 author alone allows ; the chapters on the sphere and cone 

 contain no figures at all, and a student will find no suggestions 

 for drawing a sphere or representing points on its surface. 



GEOLOGY. 



Tlic ]i itluini and the Ancastcr Gap. a Study of River 



Action. — By F. M. Burton, F.G.S.. F.L.S. 31 pages. 



4i-in.X7-in. 



(London : — A. Brown & Sons. 1/- net.) 



r/ie Winding Course of the River Wye.— By T. S. ELLIS. 



10 pages. Sj-in. X 8o-in. 



(Gloucester: — John Bellows. 1 ■ net.) 



In Mr Burton's interesting booklet the theory of river origin 

 we owe to the genius of Professor W. M. Davis is applied 

 with signal success to the origin and history of the Witham and 

 adjacent rivers, as it was also applied in the author's earlier 

 brochure on the River Trent. The Witham is a remarkable 

 river, which, rising near Oakham, first flows northward past 

 Grantham to Lincoln, and then makes an abrupt turn to the 

 south-east, entering the Wash near Boston. Excluding the 

 very recent lower portion from Lincoln to Boston, Mr. Burton 

 divides the river into three parts, — a tributary stream from its 

 source to Grantham ; a relic of an original transverse river 

 (supposed to be the primeval Devon) from Grantham to 

 Barkston ; and again a tributary stream from Barkston to 

 Lincoln. The original stream, the Devon, flowing east, cut 

 out the Ancaster Gap, after which it was captured by the 

 Trent, bringing the modern Witham into existence. There 

 were several minor vicissitudes, well worked out by the author, 

 before the Witham assumed its actual present course. The 

 pamphlet would have been easier reading if a map illustrating 

 the history of the river system had been included. Mr. Ellis, 

 however, will have nothing of Professor Davis and consequent, 

 subsequent or obsequent streams. His theory of river 



origin seems to be that of the evolution of principal channels 

 out of a network of streams occasioned by the original 

 irregularities of a land-surface newly arisen from the sea. He 

 finds illustrations of the process in the water-channels on a 

 gravelled or macadamized slope. The sinuosities of the Wye, 

 for instance, are regarded as relics of an original network of 

 channels. Mr. Ellis rejects the principle of stream capture, on 

 the ground that he is unable to conceive of a stream working 

 headwards and thus extending its valley backwards. He finds 

 special difficulty in the case of valleys with low flat divides 

 between streams falling in opposite directions, and beheves 

 that these valleys have always been excavated by the 

 continuous flow of a body of water in one direction. Whilst 

 some of these valleys may have been cut in this way as a stage 

 in the development of a river system, the divides may have 

 been smoothed by glaciers or by glacial lake overflows ; and it 

 must be remembered that low flat divides are characteristic of 

 mature and ancient topographies. The paper is illustrated by 

 a map of the Severn-Wye river system. 



PHOTOGRAPHY. 



Photography in Colours. — By George Lindsay Johnson, 



M.A., M.D.,"b.S., F.R.C.S. 143 pages, whh 8 plates in 



colour. 7i-in. X5-in. 



(Ward & Co. Price 3/-.) 



The author states that he has separated Colour Photography 

 from Photographic Optics when revising his work on the 

 latter subject, and we cannot but feel that the separation is an 

 advantage : there was. indeed, no reason for ever including 

 two sucli distinct subjects within the covers of one text-book. 



The present volume is, on the w^hole, a considerable advance 

 on the treatment of the subject in the earlier work ; the author 

 has collected together the information which has been published 

 by other workers, and has appended his own opinions to their 

 conclusions. 



This method occasionally leads to remarkable results, as 

 when a solution of " Xyline red " is stated to be a nearly pure 

 blue in colour ; but, on the whole, the book is free from serious 

 mistakes. On the screen plate processes of colour photo- 

 graphy the book is very complete, but the short chapter on 

 other processes is practically useless; it is far too scrappy and 

 brief in its treatment. Incidentally we do not think that 

 F. E. Ives ever claimed to have discovered "the principle of 

 three colours being used to reproduce all colours." Ives 

 invariably claims that the originator of the true theory of 

 colour photography was Clerk Maxwell. We note with regret 

 that the author prints his spectrum diagrams with the red to 

 the left. 



NOTICE.S. 



WEBSTER'S NEW INTERNATIONAL DICTIONARY. 

 — We have before us the details of the new dictionary which 

 Messrs. Bell & Sons are publishing. As a matter of fact it 

 is really a new work, for there are four hundred tliousand 

 references as against one hundred and seventy thousand in 

 the previous dictionary which bore the same name. Very 

 special attention has been given to the many new words which 

 science has introduced into our modern vocabulary. Although 

 there are two thousand seven hundred pages, and six 

 thousand illustrations, the whole of these are contained in one 

 volume, which is issued at a reasonable price. The dictionary 

 is likely to meet the requirements of many of our readers, who 

 can obtain all particulars on filling up and sending in the 

 special coupon to be found on page iii of this issue. 



CATALOGUES. — Among the many catalogues whicli we 

 have received is one of lantern slides sent by Messrs. Flatters 

 and Garnett, and we would call special attention to the photo- 

 graphs illustrating British Plant Associations, by Mr. W. B. 

 Crump, whose ecological work is well known. CJf special 

 scientific interest also are the photomicrographs by Mr. W. T. 

 Haydon, illustrating the reproduction and development of 

 Pinus sylvestris. 



As usual, the classified list of second-hand instruments 

 which Mr. C. Baker has for sale or hire, is useful 



and exhaustive, seeing that it runs to eighty-two pages. 

 From Messrs. R. & J. Beck, Ltd., comes a special new 

 catalogue of physical apparatus. Among some of the more 

 important pieces are optical benches for the testing of 

 photographic lenses as well as those which are used for 

 spectacles. There are also some glass troughs of useful and 

 various shapes which can be adapted to many purposes. 



A MICROSCOPIC EXHIBITION.— Messrs. Watson and 

 Sons, Ltd.. 313, High Holborn, have sent us particulars of an 

 Exhibition of Microscopic Objects which -they are holding to 

 enable microscopists to see for themselves the great diversity 

 of objects which they ofter. 



In order that the whole of the contents of their cabinets 

 may be easily examined, different subjects are set out week 

 by week so as to be readily glanced at and subsequently 

 examined microscopically. 



Two of these Exhibitions have already been held and the 

 current one from the 30th of January to the 8th of February, 

 is of Botanical Subjects. Fungi, Algae and so on. 

 Future dates and subjects are : — 



F'ebruary 13th to 22nd, Geological and Entomological 



Specimens, Objects for Polariscope. 

 February 22nd to March Sth, Mounted Pond Life, ' 

 Marine and Zoological Specimens. 



