June 24, 1909] 



NATURE 



one page of it which can be understood by a person 

 who lias not already made a study of higher mathe- 

 matics. Every now and again it seems to strilie the 

 author that he is philosophising over the head of his 

 reader, and for a moment he drops low enough to be 

 understood by a chemist who has given more than 

 the usual time to mathematics, but it is only for a 

 moment. Naturally, he does not mention dy/dx until 

 he has quite finished his treatment of curves by 

 analytical geometry, and the time of vibration of his 

 simple pendulum is given as an infinite series. He 

 does not show anywhere that he knows the problems 

 to which the chemist, physicist, or engineer would 

 apply his mathematics. He does not seem to know 

 that there are mathematical principles underlying 

 thermodynamics and the flow of heat and problems 

 in electricity which he might have referred to. The 

 harm done by such a presentation of the subject is 

 incalculable ; it gives a student the notion that he 

 cannot possibly learn to use mathematics, whereas we 

 know that almost any person can be taught to use 

 the highest kind of mathematical weapon with con- 

 fidence and security. J. P. 



Problemc der Protistenkiittde. I. Die Trypanosomen 

 ihre Bcdetitiing fiir Zoologie, Medizin mid Kolonial- 

 wirtschaft. By Prof. F. Doflein. Pp. 57. (Jena : 

 Gustav Fischer, 1909.) Price r20 marks. 

 I\- this monograph Prof. Doflein deals in a simple 

 and non-technical manner with an important group 

 of protozoan parasites, the trypanosomes, in parti- 

 cular those which cause important diseases of man 

 and animals, such as sleeping sickness of man, and 

 nagana, surra, and dourine of horses, &c., so that 

 the medical man without special zoological know- 

 ledge can readily understand the subject. 



The author considers that there is little or no 

 evidence that these trypanosome parasites leave the 

 bodv of the host in an encysted or sporulating form, 

 which may then re-enter the body and cause infec- 

 tion. Infection generally occurs through the agency 

 of an intermediate host, or, in the case of dourine, 

 by direct contact. He regards the reputed encysted 

 forms as probably the result of degenerative changes 

 in the parasite. The observations of Schaudinn on 

 the supposed transformation of certain intracellular 

 parasites of birds into trypanosome forms are dis- 

 cussed, and considered to be probably erroneous. 

 After discussing the possible evolution of these para- 

 sites, the author concludes with some remarks on the 

 ■economic importance of the diseases they produce in 

 the colonies. The book is very readable, and is well 

 illustrated. R. T. H. 



American Philosophv : the Early Schools. By Prof. 



I. W. Rilev. Pp-. x + 595. (New York: Dodd, 



Mead and Co., 1907.) 

 This rather bulky volume is the first of a series in- 

 tended to give an historical summary of the progress 

 of philosophical thought in America. The European 

 reader must have an unusually determined interest in 

 the history of speculation if, from the purely philo- 

 sophical point of view, he is willing to follow Prof. 

 Riley in his studies of minor thinkers, whose names, 

 ■except in a few cases, will probably be entirely 

 unknown to him. Regarded from a wider point of' 

 view as a study of the earlier development of the 

 " soul of a people " that has come to fill so important 

 a place in the modern world, the book will be found 

 "both valuable and interesting. 



Prof. Riley has taken advantage of his three years' 



tenure of the Johnston scholarship in Johns Hopkins 



University to acquire an exhaustive knowledge of his 



subject, and he presents the results of his inquiries 



NO. 2069, VOL. 80] 



lucidly and attractively. After a brief historical survey 

 and a still shorter essay on the relations between 

 American philosophy and American politics, he de- 

 velops in five successive " books " the history of the 

 several movements — philosophical or religious — to 

 which the thinkers of his period are related. 



Of these movements the only one with which the 

 philosophical student will, as such, feel much concern 

 is early American idealism, which is decorated by the 

 names of Samuel Johnson (of Connecticut) and 

 Jonathan Edwards. Both these writers have relations 

 with Bishop Berkeley, " the only European philo- 

 sopher of the first rank who visited the colonies." 

 Students of Berkeley already know that Johnson was 

 his avowed admirer and follower, but they will be 

 glad of the much fuller light which Prof. Riley has 

 thrown upon the dealings of the two philosophers with 

 one another. In the case of that remarkable man, 

 Jonathan Edwards, Prof. Riley makes it manifest that 

 his idealism was an independent development from 

 Locke — a development the main positions of which 

 Edwards reached at some time between his thirteenth 

 and his sixteenth years ! 



The scientific reader will be tempted to give special 

 attention to the pages on Benjamin Franklin, who, 

 as "a kind of Socrates in small clothes," pla\'ed an 

 interesting if not imposing part in American deism, 

 and will be reminded painfully of the bitterness of 

 English intolerance in the eighteenth century when he 

 comes upon the name of Joseph Priestley among the 

 apostles of American materialism. 



The Photography of Coloured Objects. By Dr. C. E. 



Kenneth Mees. Pp. vi + 69. (Croydon : Wratten 



and Wainwright, Ltd., 1909.) Price is. net. 

 Dr. Mees being a partner in the well-known photo- 

 graphic firm of Wratten and Wainwright, and' writing 

 on a subject most intimately connected with the manu- 

 factures of the firm, naturally refers almost entirely 

 to the plates and colour filters that he is most in- 

 terested in, but the volume is in no sense, or in any 

 part of it, a trade advertisement. The author explains 

 in a clear and straightforward way the details of the 

 subject, and the chapters on "portraiture," "land- 

 scape photography," and " the photography of coloured 

 objects for reproduction " have been produced by the 

 aid of several authorities who devote themselves to 

 these branches of work. 



Many will be surprised to see the great advantage 

 in photographing polished mahogany attainable by the 

 use of a panchromatic plate and a red screen, as com- 

 pared with the. result obtained b\' an ordinary plate. 

 The latter emphasises the scratches and other surface 

 imperfections and hardly shows the grain, while the 

 panchromatic plate gives what is obviously the natural 

 appearance of the wood. For the correct representa- 

 tion of ordinary coloured objects, the general advice is 

 to use a panchromatic plate and a rather deep yellow 

 screen. M. Callier, in a note that he contributes, 

 points out the practical shortcoming of the ordinary 

 orthochromatic plate (erythrosin type) in the photo- 

 graphy of open meadows and pine-trees. The green 

 of the pines falls just into the gap of deficient sensitive- 

 ness in the spectrum, while the green of the meadows 

 corresponds to the maximum of green sensitiveness; 

 hence there is obtained an exaggerated contrast which 

 no ordinary yellow screen will correct. 



The author deals also with the suppression of certain 

 colours, as in the photography of stained documents, 

 the increase and decrease of contrast in coloured 

 objects, as in photomicrography, and with three-colour 

 photography, that is, so far as plates and colour 

 screens are concerned. Although the volume is small 

 it deserves an index. 



