296 



NATURE 



£May 5, 192 1 



creature's movements are due to contractility of 

 the ectoplasm is followed (in one instance, on 

 p. 17, where this matter is discussed, "endo- 

 plasm " seems to have been printed by mistake). 

 Turning- to the chapters on Vertebrata, it will be 

 found that Ridewood's researches on the develop- 

 ment of vertebrae have been u-tilised ; these, as is 

 pointed out in the preface, "have narrowed the 

 gap between the so-called arco-centra and chorda- 

 centra." 



It is somewhat surprising to find that the paired 

 serial excretory tubes of the Peripatids are still 

 described as coelomiducts, in spite of Miss Glen's 

 recent demonstration (carried out under Prof. 

 MacBride's auspices) that they are true nephridia. 

 This discovery renders the retention of the group 

 in a "class Antennata," which includes also Milli- 

 pedes, Centipedes, and Insects, the more un- 

 natural. 



As one turns over again the pages of this 

 volume the clearness of the descriptions and the 

 excellence of most of the 360 illustrations afford 

 Renewed pleasure. In a future edition some of 

 the representations of insects might be replaced 

 with advantage ; no entomologist would recog- 

 nise the figure that does duty for a tsetse-fly. 



G. H. C. 



Marine Engineering. [A Text-Book.) By 

 Engineer-Capt. A. E. Tompkins. Fifth edition, 

 entirely revised. Pp. xi -h 888. (London : Mac- 

 millan and Co., Ltd., 192 1.) 365. net. 



The fourth edition of this work was published in 

 191 4, a few weeks before the outbreak of the war, 

 and was reviewed in our columns in September of 

 that year. Owing to the great advancement in 

 marine engineering which has since taken place, 

 a large part of the book has been rewritten, and 

 the remainder thoroughly revised. We are 

 specially glad to notice that room has been 

 found for a fuller consideration of mercantile prac- 

 tice, since this will have the effect of bringing the 

 merits of the volume before a greatly enlarged 

 class of readers. The section on turbines now 

 covers three chapters, and includes an adequate 

 discussion of geared turbines and auxiliaries. The 

 latest systems of oil-firing are included, and the 

 section on internal-combustion engines has been 

 enlarged, and embraces both submarine and mer- 

 cantile engines. 



The labour of revising a comprehensive treatise 

 such as the volume before us must have been very 

 great, especially when one remembers that the 

 author was on war service supervising repairs 

 both at home and in Italy ; the experience he 

 gained during those years is embodied in the 

 volume, and adds greatly to its value. The book 

 is primarily intended for sea-going engineers, and 

 therefore contains nothing in the way of mathe- 

 matical fireworks. Sufficient of the theory Is in- 

 cluded to enable the reader to understand clearly 

 the principles underlying the working of the 

 machinery which the marine engineer is called 

 upon to handle. The book contains a very large 

 NO. 2688, VOL. 107] 



number of admirable drawings, , and these, to- 

 gether with the clear descriptions, render the 

 volume of value to all connected with marine en- 

 gineering. There is also a large collection of 

 examination questions at the end of the volume; 

 numerical answers are appended to these. The 

 impression given by the volume, however, is that 

 it is not a cram book for examinations, but a care- 

 fully thought out scheme which will add greatly 

 to the knowledge of the engineer. 



An Introduction to Technical Electricity. By 

 S. G. Starling. Pp. xii-|-i8i. (London: Mac- 

 millan and Co., Ltd., 192 1.) 35. 6d. 

 This little work is one of a series designed for use 

 in continuation classes and central schools to form 

 the first stage in specialisation in the direction of 

 electro-technics, and necessarily treats the subject 

 in an elementary way intermediate between the 

 scientific an^ the practical. With the exception 

 of a brief mention of the transformer, only con- 

 tinuous currents are dealt with, and only the very 

 simplest mathematics are required. The concep- 

 tion of the electric current is very suitably intro- 

 duced by simple experiments with dry cells, and 

 commendable features of the method by which the 

 subject is developed include the leading up to the 

 permanent magnet through the electro-magnet^ 

 and making the student familiar with the effects of 

 a current before he is bothered about details as to 

 its production. On the whole, however, we should 

 have liked to see a little more continuity of idea 

 in the treatment. Practical applications are kept 

 well in view all through, and, in spite of a few 

 minor inaccuracies of engineering detail, form 

 adequate illustrations of the principles. Lamps 

 and lighting, motors and dynamos, and the tele- 

 phone are briefly explained, and, as might be ex- 

 pected, electrostatics do not come within the pur- 

 view of the treatment. 



Set of Cards for Teaching Chemical Formulae and 

 Equations. Devised by Mrs. M. Partington. 

 (London: Baird and Tatlock, Ltd., n.d.) is. 4^. 

 This is a set of cardboard pieces printed with the 

 symbols of elements and common radicles, and 

 graduated in size according to predominant 

 valency ; positive radicles are blue, negative are 

 pink. The formulae are made up by placing the 

 appropriate elements or radicles side by side. It 

 is at once evident that ferrous •phosphate is 

 Fe3(P04)2, and ferric phosphate FeP04, while such 

 combinations as CaCl or NaCl2 appear wrong at 

 once. The idea, so far as it goes, is ingenious, 

 and a great deal of facility in writing formulae 

 may be gained by an exercise more like play than 

 work ; moreover, the method cannot foster the 

 misconception of rigid bonds. It is suggested that 

 the pieces can be used to make constitutional 

 formulae — sulphuryl chloride and sulphuric acid 

 are given as examples. It is evident, however, 

 that before pupils get to the stage of considering 

 the relation of these compounds, the device should 

 have served its purpose; 



