4-12 



NATURE 



[September 28, 191 1 



ticularly well-adapted agent for the working of such 

 machinery. A modern book on cranes becomes thus 

 quite naturally a book on electric cranes. 



Mr. Hill's work is a thoroughly practical treatise 

 on electric crane construction. The subject is so com- 

 plicated and so many-sided that any attempt to treat 

 it in a general way must be unsatisfactory, and the 

 author has wisely decided to represent his subject 

 rather by means of well-chosen examples of successful 

 work than by a general treatise. The importance of 

 scientific principles is, however, not overlooked; inter- 

 leaved with the descriptive matter we find the neces- 

 sary calculations as to stresses, stability, power re- 

 quired, action of brakes, and other matters capable of 

 scientific treatment. The examples chosen comprise 

 various forms of overhead travelling cranes, locomotive 

 and portable jib cranes, derricks, sheer legs, trans- 

 porters, revolving cantilever cranes, and cableways. 

 Then follows a chapter on the power required for 

 crane driving. From tests quoted by the author, it 

 appears that the efficiency in many cases is remark- 

 ably high, reaching nearly 70 per cent. 



In discussing starting torque and acceleration, the 

 author also quotes from practical experience for hoist- 

 ing, lowering, travelling, and slewing. Chapter x. 

 deals with the design of crane structures. Here we 

 find discussed the strength of struts, both on the 

 basis of Euler's and Rankine's formulae, the strength 

 of lattice girders and various types of beams gener- 

 ally, the construction of cantilevers and cognate 

 matters, all exemplified by very full diagranls and 

 working drawings. 



The following three chapters deal with design of 

 machinery, frames, bearings, axles, and drums, brakes 

 and toothed gear. Especially the last-named subject 

 is very fully treated, including the question of per- 

 missible wear and the use of worm-gearing. Most 

 readers will be surprised at the high efficiency obtained 

 bj this mode of driving, when the worm runs in an 

 oil bath. The explanation given by the author is that 

 metallic contact between the teeth does not take place, 

 since the film of oil between the surfaces is not 

 squeezed out even at very heavy pressure. This has 

 also been the experience of motor-car designers who 

 find for worm-drive efficiencies well above 90 per cent. 

 After a short chapter on hooks, ropes, and chains, 

 we come to the electric and magnetic details begin- 

 ning with the design of magnets. It is to be regretted 

 that the author has adopted the hybrid system of 

 units where induction is given as so many c.g.s. 

 lines per square inch. In working with such a system 

 one loses completely the connection with first prin- 

 ciples, and the solution of any problem becomes simply 

 a matter of blindly applying certain formulae. As 

 regards motels, the author deals very fully with the 

 question of rating as influenced by the intermittent 

 service, and he shows that crane motors should, as 

 regards mechanical strength and commutation, be 

 designed for the full load, but as regards heating foi 

 a verj much 1 educed load. Only D.C. motors are dis- 

 cussed, the author holding that A.C. motors are un- 

 suitable for crane work. This is perhaps too sw 

 a condemnation. In many docks on the Continent 

 NO. 2187, VOL. 87] 



polyphase motors an used, and with the advent of 

 the A.C. commutator motor there is given every 

 facility for using alternating current where no con- 

 tinuous current is available, and the author's recom- 

 mendation of installing a converter for the power 

 supply to the cranes becomes a useless complication. 



A table on p. 302, giving from practical experience 

 the annual working cost of seven different cranes, is 

 very interesting. It shows that the cost of power 

 taken at V$A. per unit is negligibly small. It amounts 

 in the worst case to only 1*3 per cent, of the total 

 cost, and in most cases it is about 1 per cent. Thus, 

 with current purchased even at the usual lighting rate 

 of about 4<i. per unit, the cost of power is quite in- 

 significant. This is due to the fact that the load factor 

 of a crane is exceedingly small. The total energy 

 given off by all the crane motors per annum only 

 represents full output over about twenty to seventy 

 hours per annum. The annual cost is almost entirely 

 made up by interest, depreciation, and repairs, ana 

 the problem to be solved by the designer of cranes is 

 not so much the saving of current as the production 

 of a cheap and robust design. 



Gisbert Kapp. 



MORPHOLOGY OF THE VERTEBRATES. 

 Elements de Morphologic des Ycrtcbres. Anatomie 

 et Embryologie Companies, PaUontologie et Classi- 

 fication. By Prof. L. Vialleton. Pp. xiv + 790. 

 (Paris: Octave Doin et Fils, 1911.) Price 18 

 francs. 



THIS is an interesting and thoughtful introduction 

 to the morphology of the vertebrata, very 

 clearly written, well illustrated, and with several dis- 

 tinctive features. The author thinks, probably with 

 justice, that the vertebrata are better subjects than 

 the invertebrates for the illustration of morphological 

 principles. Their structure is more thoroughly known 

 and its relations to the conditions of life are more 

 certain ; the development of the chief types has been 

 worked out in its main features; and we have, on 

 the whole, more information in regard to the past 

 history. Filiation is clearer among vertebrata than 

 among invertebrates. For learning the lessons of 

 morphology it is better to begin with one 

 phylum than with many, and the most educationally 

 profitable phylum is that with which students are 

 likely to be most familiar — the vertebrata. 



The plan of the book is as follows. After an intro- 

 duction dealing with general concepts such as homo- 

 logy, the author devotes the first part to general 

 embryolog) - tin germinal layers, the early primordial 

 and the fundamental architecture of head and trunk 

 and limbs. The second part deals seriatim with all 

 the systems and organs, from the skin to the gonads 

 treating 1 verything comparatively and embryologicallyj 

 It is all very clear and careful, but in a book of the 

 dimensions ol tltis .»nc we look for rather more cri- 

 ticism. To take but a single instance, we think 

 Vialleton 's conventional account of the pectoral 

 skeleton <>t the Monotreme, with its episternum and 

 absence of procoracoids, might have been improved 

 without risk el dogmatism. We may notice hew that 



