278 



KNOWLEDGE. 



[December 1, 1900. 



a work for the serious and advanced zoological student ; and 

 from this point of view is everything that can be desired. 

 Without for one moment underrating the excellent, systematic 

 work of the three gentlemen whose names ap])ear on the title- 

 page, it must be acknowledged that the great feature of the 

 present volume is the exhaustive essay by the editor on the 

 " Cieloni." Those of our zoological readers who have reached 

 middle age will recollect that in their college days they were 

 taught that the pleuroperifoueal cavity of the higher animals 

 was formed by the splitting of the mesoblastic layer of the 

 eml^ryo, so that the cavity in question was in no sense a 

 morphological unit. Professor Lankester now demonstrates in 

 the clearest manner how the coelom (as the pleuroperitoneal 

 cavity is now termed^ is developed as a i)air of buds from the 

 primitive intestinal tract, and is originally a receptacle for the 

 internal generative organs. It is therefore essentially a mor- 

 phological factor of prime importance in the animal series, and 

 one which justifies the separation of animals of higher grade 

 than the sponges into two divisions, according as to whether the 

 coilom is or is not differentiated as a distinct cavity. "Whether, 

 however, the names " Enterocoela " and " Crolomocojla " are 

 the happiest that could have been selected for the groups in 

 question is one on which a difference of opinion may be 

 permissible. To follow the editor through his account of the 

 history of the realisation of the true nature of the crelom (an 

 investigation in which he himself has played a leading part) 

 would manifestly be impossible on the present occasion. But 

 we may draw the reader's attention to the admiral)le description 

 of the diminution of the size of this cavity in the Mollusca and 

 Arthropoda, and the proportionately large development of the 

 blood-vascular system at its expense. And mention should 

 likewise be made of the remarkable investigations by Mr. 

 Goodrich concerning a communication between thecadomioand 

 blood-vascular systems in the leech. Following on this epoch- 

 making essay, which forms Chapter II. of the entire work, 

 Mr. Slinchin describes in an excellent manner the sponges : 

 while in Chapters IV. and Y. Mr. Herbert Fowler discusses 

 those polyps which used to be called Hydrozoa, Jlr. Bourne 

 being responsible for the Sea-anemones, Corals, and Ctenophora, 

 to which the two final chapters of the volume are devoted. A 

 feature of the volume is the beauty and excellence of the 

 illustrations, which have for the most part been prepared 

 expressly for the work, and all of which are admirable examples 

 of the manner in which minute structures should be figured. 

 In only one case (Fig. 11, ]i. 20) have we noticed a discrepancy 

 between the lettering of the figures and the accompanying 

 description, and there it is but slight. Another feature is the 

 presence of a separate index to each section of the work. To 

 some readers, at any rate, the addition of a glossary would be a 

 distinct advantage : but this is the only improvement we can 

 suggest on what is in every way an admirably conceived and 

 admirably executed undertaking. 



A Romancer's Local Colour. By S. E. Crockett. (Xew- 

 man and Guardia.) That innumerable host of very amateur 

 photographers who affect to find pleasure in chasing, and, as 

 they express it, '" snap-shotting " men and objects, is rapidly 

 becoming a nuisance to the more retiring and modest section of 

 the community. A perusal of this light and huniorous pamphlet 

 may, perhaps, infuse some purpose into the methods of such 

 photographers. It is scarcely necessary to add that, unlike the 

 methods, cameras need not be changed — for, of course, the 

 eminent novelist is, in his own words, "no special pleader" for 

 the wares of Messrs. Xewman and Guardia. 



TiiK Scientific Foundations of Anai.ythal Ciikmistry. 

 2ud Edition. By W. Ostwald, rii.D. (Macmillan.) Gs. net. 

 Prof. Ostwald is well known as author of several valuable 

 works on chemistry and chemical philosophy, and as a proof of 

 his popularity among advanced students it is only necessary to 

 mention that the first edition of the volume under notice has 

 been translated into four languages. The book will commend 

 itself to all who wish to know the why and the wherefore of the 

 reactions which take place in the multifarious operations of the 

 chemical laboratory. Our author says "a scientific foundation 

 and system of analytical chemistry have hitherto failed us 

 because the general knowledge and laws necessary for these have 

 not been at the disposal of scientific chemistry itself. It is only 

 within the last few years that it ha.s become possible to elaborate 



a theory of analytical reactions.'' Prof. Ostwald is to be con- 

 gratulated on the production of tliis book, which enables the 

 student to work out his analyses, not by rule-of-thumb, but 

 in an intellectual manner. The book does not pretend to be 

 compreheu.sive, and, indeed, there is plenty of scope for ampli- 

 fication. The subject up to the present time has received scant 

 attention at the hands of analytical chemists. Dr. M'Gowan 

 has succeeded in suppl3'iDg an able English translation. 



A Handi'.ook of PitoTOGRAPHy IN Colours. By Thomas 

 Bolas, Alex. A. K. Tallent, and Edgar Senior. (Marion & Co.) 

 Illustrated. 5s. It is interesting to note that the firm of 

 Marion & Co. were the first to publish a work on trichromatic 

 photography. At that time (thirt3-one years ago) the process was 

 in its extreme infancy, but now photography in colours may be 

 said to be an accom])lislied fact. A perusal of the volume before 

 us convinces us that an exhaustive treatise on this late develop- 

 ment of the photographic art has at last been made available to 

 the public. The work is divided into three sections, one of 

 which is credited to eacli of the three authors respectively. In 

 the first section a history of three-colour work, and a general 

 survey of the many processes of colour photograjihy, is presented, 

 and it will be surprising to man}- to learn that the art of 

 producing photographs in colours was carried out in a very crude 

 fashion long before ordinary photography came into general use. 

 In the next section, which is the largest in the book, instructions 

 are given for carrying out experiments in colour photography. 

 They were compiled from lecture notes made by Mr. Tallent 

 for use in the Polytechnic classes, and will be valuable to those 

 who wish to acquaint themselves with the practical details of 

 the art. The remainder of the volume is occupied with a 

 description of Lippman's Process of Interference Heliochromy. 

 It was in 18',ll that Lippmann, a French physicist, announced 

 that he had been able to take direct photographs in the camera 

 showing the spectrum in the true colours, and since that time 

 rapid progress h.as been made. 



" A.stronomical and Physical Researches made at Mr. 

 AVilson's Obskrvatoi'.y, Daramona, West-MEatm." There is 

 one type of observatory which seems almost peculiar to the 

 British Isles. Private observatories there are in ]ilenty in other 

 countries, well-equipped, and more or less well-financed by 

 wealthy men, and extremely well worked by able astronomers, 

 but in the British Isles we find, over and over again, that the 

 amateur astronomer of means not onl}' equips the observatory 

 and provides for the carrying on of the observations, but is also 

 himself the worker, giving his brain, and, it may be, his all too 

 scanty leisure to the furtherance of his science. The observations 

 at Daramona have been carried out solely by 'Sir. "Wilson and 

 the occasional assistance of his personal friends, Dr. A. A. 

 Rambaut. Prof. Fitzgerald, Prof. G. M. Minchin. and Mr. P. L. 

 Gray. They are practical researches into the difficult problems 

 of solar physics where <( priori reasoning becomes worse than 

 useless, since it is impossible to realise the actual conditions in 

 a laboratory. The principal instruments used were a 24-inch 

 silver-on-glass mirror of 10-S feet focus, a large polar heliostat 

 having a plain silvered mirror of l.j inches diameter, a 

 modification of Prof. Joly's meldometer. and a modification of 

 Prof. Boys' radio-micrometer. Perhaps the most important and 

 fundamental series of researches carried out were those on " the 

 effective temperature of the sun." Here the general idea 

 was to endeavour to huJance the heat of the sun by means of an 

 artificial source of heat at a high known temjierature, and the 

 method employed w.as jiurposely simple. Taking Angstrom's 

 estimate of the loss in the earth's atmosphere, and the probable 

 loss in the sun's atmosphere, as found in the paper by Mr. 

 Wilson and Dr. Rambaut, on " The Absorption of Heat in the 

 Solar Atmosphere," the effective temperature of the sun comes 

 out as between SOOO" C. and lO.OUO" C. In the paper by Mr. 

 AVil.son and Prof. Fitzgerald on ''The Effect of Pressure on the 

 Temperature of the Crater of an Electric Arc," a suggestion is 

 made which bears, perha]is, on the cause of opacity in the solar 

 atmosphere. The arc and the surrounding atmosphere were 

 enclosed in a steel tube, closed at its end by a lens, and when 

 the atmosphere was under great pi'essure, powerful convection 

 currents were set up, and these currents scattered the light just 

 as snow does, or any finely-divided transparent body immersed 

 in another of a different refractive index. Light trying to get 

 through is rettected backwards and forwards in every direction, 



