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opinion there are two objections: one, that with the Coronula once fixed in the whale's soft skin, more irritation would probably be caused by rubbing it off than by leaving it alone; the other, that the soft-stalked Lepadid Conchoderma so curiously and prominently planted on the Balanid implies that the Coronula is a place of exceptional security.

not been previously figured. An economy now commonly practised, and no doubt very necessary, shows the wings only of one side. This should redeem from heartless ridicule the proverbial pig with only one ear, but by depriving the moth or butterfly of its bilateral symmetry it makes it somewhat of an artistic failure. A carcinologist is apt to find variation in colour-marking very untrustworthy for specific distinction. The en(5) Dr. G. A. Boulenger's fine catalogue of tomologist, on the other hand, appears to rely fresh-water fishes of Africa is now continued in upon it with considerable confidence.

(2) This is further exemplified in Mr. Claude Morley's revision of the Ichneumonidæ, although, so far as illustration goes, that work is in striking contrast to the generous treatment of the Lepidoptera. For Part iv., with more than forty new species, has only a single figure. This one example, however, is furnished with the full complement of wings, antennæ, and hexopodal appurtenances, and is to some extent suggestive of the "remarkable grace and beauty, combining delicacy of outline with both fine and brilliant, not infrequently metallic, coloration," which Mr. Morley claims for the objects of his study. It is rather unfortunate that the plate unmistakably shows an insect in which the wings have each a brown band and brown apex, while the Joppa nominator, Fabricius, which it is said to represent, is described by Fabricius as having "alis omnibus fascia apiceque nigris" ("Ent. Sys.," vol. ii., ("Ent. Sys.," vol. ii., p. 158, 1793). Mr. Morley reveals without explaining the discrepancy.

(3) Prof. Bezzi's work on the African Diptera of the family Syrphidæ is less abstemious in the matter of illustrations, and, besides a useful explanatory diagram, furnishes very full and important keys for the discrimination of the genera and species. Mr. C. J. Gahan's verdict may well be accepted that the present treatise "greatly advances our knowledge" of the group. There are said to be about 2300 described species, and the difficulty of dealing with them is attested by E. Brunetti, who some years ago said of the genus Syrphus, "this genus I do not touch upon at present in view of the large number of supposed species described from Oriental regions, and their close affinities" ("Records Ind. Mus.," vol. ii., p. 57, 1908).

(4) Passing now from the air to the water, it will be found that Mr. D. G. Lillie gives as many illustrations of the Cetacea as could be expected from his opportunities, seeing that he starts with the acknowledgment that the Terra Nova "did not succeed in capturing any specimens of this group." He mentions the belief of whalers that humpback whales rub themselves against rocks to get rid of the Balanid Coronulae. To this

a third volume, with promise of a fourth. The species described are 394, and there are 351 textfigures, 45 of them species not in the British Museum collection. It is pleasant to observe that for the Muraena anguilla of Linnæus Dr. Boulenger accepts the name Anguilla vulgaris, Turton, in place of the barbarous tautology in which some authorities delight. In dealing with the Cichlidæ, which occupy three-fourths of the present volume, he is forced to admit that Nature is sometimes very ill-natured to the conscientious systematist, spoiling the best-laid schemes of classification by a very inconvenient interlacing of characters. This appearance, however, of what our distant cousins call Schadenfreude is not due to a pure delight in mischief, but is the simple result of that universal consanguinity in which the sincere evolutionist is bound to believe. In a synopsis of 41 genera, and a further synopsis of a genus with 94 species, there are pretty sure to be some entanglements. To lovers of odd fishes, Psettus sebae may be commended, with its "body deeper than long," a species figured life-size by Seba as Chaetodon quadratus. The mouth of Corematodus shiranus, Boulenger, must be useful for hygienic mastication, but disagreeable to its prey, as its massive jaws are fitted with "extremely broad bands of innumerable minute club-shaped teeth."

(6) In Mr. Preston's treatise, "wherever possible, illustrations of hitherto unfigured species have been given." The author regrets that he

can, in most instances, only deal with the shells of the species quoted," material for anatomical work not being available. But in his Introduction he is able to give several interesting bionomic notes, and for the anatomy of one species, Mulleria dalyi, Smith, he has a sad satisfaction in quoting largely "from the late Mr. Martin F. Woodward's invaluable Paper on the subject." In some of his references Mr. Preston leaves the student rather in the dark. Thus he cites :-"Theodoxis, de Montfort, Conch. Syst., ii., 1810, p. 350; Neritina, Lamarck, 1822 [Neritine, 1809]. Type, T. lutetianus, de Montfort (fluviatilis, Linn.)", without saying whether Neritine is French or Latin, or where it is to be found, and without showing that p. 350 in de Montfort is only a plate,

while the description of genus and species on p. 351 gives the authoritative spelling in the name Theodoxus lutetianus.

(7) The numerous new species described in Mr. E. A. Smith's treatise are illustrated in two excellent plates. Mr. Smith's mastery of the subject almost forbids criticism, but may still excuse inquiry in regard to his use of the generic names Rissoia and Panope. In the "Discovery" Gastropoda, 1907, he transferred without explanation his Rissoa adarensis to Rissoia. Under Rissoia adarensis (Smith) he now adds a note: “A synonym of Rissoa is Apanthausa, Gistel ('Naturgesch. Thierreichs,' 1848, p. x)," without explaining what is the relationship of Apanthausa to Rissoia. In 1850, Gistel in the " Handbuch der Naturgeschichte," p. 554, declares that Rissoa must be changed (though he does not say why) into his Anatasia, the date of which is given by Scudder as 1848. Neither Gistel in 1850 nor Scudder later on makes any mention of Apanthausa. A further perplexity is caused by Mr. Smith's change of Panopaea zelandica, Quoy and Gaimard, into Panope zelandica, without any reference to show that Panope, as the name of a molluscan genus, antedates its use in 1813 by Leach for a genus of Crustacea. Les "Panopes," Lamarck, Ann. du Mus. Paris, vol. x., p. 394, 1807, is a French term.

T. R. R. STEBBING.

CHIEFLY MONGIAN GEOMETRY. (1) Descriptive Geometry for Students in Engineering Science and Architecture. A Carefully Graded Course of Instruction. By Prof. H. F. Armstrong. Pp. vi+ 125. (New York: J. Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1915.) Price 8s. 6d. net. (2) Geometry of Building Construction: Second Year Course. By F. E. Drury. Pp. xii+226. (London: G. Routledge and Sons, Ltd., 1915.) Price 38. net.

(3) Practical Science and Mathematics. By E. J. Edwards and M. J. Tickle. Pp. viii+175. (London: G. Routledge and Sons, Ltd., 1915.) Price 1s. 6d. net.

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traditions of Canada will be adopted by England. The book covers the usual ground. The problem, are based on the usual conventional figures. The book is beautifully got up, the text and figures both being admirable.

(2) This book is also on Mongian geometry. In place, however, of the conventional subjects, it treats real problems of building construction throughout. It is, in fact, intended as a builder's text-book. Just on that account it forms a suitable book for any student of Mongian geometry. The propositions of the subject presented in the abstract are too difficult for the majority of students. The treatment of the propositions as inductions from concrete problems makes them much easier to grasp and to retain. This distinction is realised by the author and forms the basis of the book, as indeed it does of the whole series. The book is certain to have a wide sphere of usefulness.

(3) This book also belongs to the excellent series edited by Mr. Udny Yule. It is concise and clear, the style simple and direct. The inductive method is wisely followed, a number of particular cases being followed by a generalised statement. It is a useful book, and avoids confusing the mind by excess of abstract reasoning. There is a generous use of graphs, and the only fault we find is the failure to emphasise the fact that the "algebraic law of the relation between two quantities" y = ax + b is only one among many possibilities.

ELECTRICAL ENGINEERING

TEXT-BOOKS.

Second

(1) A Treatise on the Theory of Alternating Currents. By Dr. A. Russell. Vol i. Edition. Pp. xiv +534. (Cambridge: At the University Press, 1914.) Price 15s. net. (2) Electrical Engineering. By Dr. T. C. Baillie. Vol. i. Introductory. Pp. vii+236. (Cambridge: At the University Press, 1915). Price 5s. net.

(3) Electrical Instruments in Theory and Practice. By W. H. F. Murdoch and U. A. Oschwald. Pp. viii+366. (London: Whittaker and Co., Price 10s. 6d. net.

(1) THE geometry of Monge, in which they (4) Alternating-Current Electricity and its Applica

plan and elevation, is one of the most educative branches of mathematics; and yet it is taught in this country only as a technical subject for engineering and architectural purposes. The secondary school is unaware of its existence. Hence the pleasure with which we find a Canadian writer on the subject reckoning that his book will be used in high schools. Let us hope that the good

tions to Industry. First Course. By W. H. Timbie and Prof. H. H. Higbie. Pp. x+534 (New York: J. Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1915.) Price

8s. 6d. net.

A

(1) NEW edition of Dr. Russell's book will be welcomed both by physicists and electrical engineers, particularly by those who

to discuss the design and construction of electrical instruments from the broadest point of view. The theory of their action and their mechanism is clearly laid down. The opening chapter contains a brief summary of the history of exact measurement together with a short account of some absolute determinations of the fundamental elecquantities. In this connection it is interesting to note that so recently as 1881 Kelvin and Bottomley stated that "the most accurate method of measuring candle power was by comparing the shadows of a pencil illuminated by the two sources." The summary shows clearly how the development of electrical instrument construction is related to the practical needs of the industry.

have to teach advanced students. The addition
of greatest interest to electrical engineers is the
chapter dealing with the theory of coupled elec-
trical circuits. This subject is now of great
importance in wireless telegraphy and a simple
and complete statement of the theory, such as that
worked out by Prof. Fleming or that contained
here, is of great value. The tables for determin-trical
ing high-frequency resistance and for estimating
the inductance of coils and for calculating the
effective capacity of a long antenna should also
be of importance to radiotelegraph engineers. It
is impossible, in a short notice, to describe
adequately the vast field of theoretical work that
the book covers, or to do justice to the masterly
treatment of the many problems with which it
deals. The book has already taken its place as
a standard work on alternating current theory,
and the additions made in this new edition will
tend to establish it more firmly in the position it
has already attained.

(2) The opening chapter of Dr. Baillie's book on electrical engineering contains a useful summary of the pioneer work on which the modern practice of electrical engineering rests. Brief reference is made to the work of Volta, Galvani, Siemens, Ampère, Clerk-Maxwell and many others. At the present time it is perhaps of interest to note that among those whose names are household words in electrical science, only two, those of Siemens and Hertz, are of Teutonic origin. The following chapters deal with the ordinary phenomena of electrical conduction, the measurement of resistance power and current, about which all elementary students in electrical engineering have to learn, together with chapters on batteries and the electric light.

Special mention may be made of chapter vii, which deals extremely well with the potentiometer and its uses, and to the chapter on batteries, which is exceptionally clear and good. The book is sufficiently elaborate to meet the needs of students taking a first year course in a technical college Some doubt may be expressed as to the value of such figures as 18, 19, 20, 21, 24, 25, 26, which show the outer cases of instruments. This, however, is a minor defect; the illustrations do not detract from the value of the book, they merely add unnecessarily to its bulk. As a text-book for elementary courses in electrical engineering it should fulfil a useful purpose, a result which is greatly assisted by the 125 examples, to be worked by the students, which are given at the ends of the chapters.

(3) The book by Messrs. Murdoch and Oschwald on electrical instruments is a welcome attempt

In an interesting chapter on damping, the general theory is laid down and discussed in connection with the instruments in which it forms an essential feature, the Grassot fluxmeter being, of course, the outstanding example. The following chapters describe the ordinary form of moving coil ammeter, electrostatic and current voltmeters, hot wire instruments, dynamometer type instruments, and energy meters. In the chapter on magnetic testing a suggestion is made to resuscitate the old magnetometer method of testing with weak fields. This method is an admirable one under suitable conditions, but in a laboratory within range of an electric tramway or railway, or even of electric light mains, it is nearly useless. There are numerous figures and results given throughout the book which have been obtained from the authors' own requirements, which are of value as independent testimony to the accuracy of the apparatus with which they have been made. The book should be a useful work of reference for those who are engaged in the manufacture of electrical instruments and in electrical testing.

(4) The book on alternating current electricity and its application to industry by W. H. Timbie and H. H. Higbie is an attempt to simplify the teaching of alternating current technology for engineering students. The teaching of this subject has advanced with great strides since the time, some twenty years ago, when the study of alternating currents was regarded as a branch of applied mathematics, to be taken after an elaborate introductory mathematical training. Alternating current work should form part of a normal second year course for all engineering students, and this book is one which should be most useful as a text-book for helping in the teaching of this subject during the early stages. The hydraulic analogies in many cases are ingenious and enlightening, and explain the apparent incon

sistencies met with in alternating current work. The only serious criticism that may be offered is that it attempts rather too much. For example, in Problem 55, on p. 275, the student is asked to calculate the self-induction of a long three-phase

transmission line, and in the next question to calculate the corresponding reactance. He might

be led to expect that this result would give him the drop of the line, whereas it does not, because the mutual induction between the lines and the difference in phase between the currents in the lines are not taken into account. One might also be inclined to criticise the amount of space devoted to the subject of armature windings for alternators. This is defended in the preface, as a useful mode of teaching polyphase current technology. In practice an oscillograph demonstration of phase differences would be much more illuminating. The order of taking up the subject, too, strikes one as rather unnatural. It is surely a mistake to leave out any reference to the physical nature of self-induction and capacity until reactance has been studied.

The argument from the concrete example to the abstract theory is much used in America and elsewhere, and possibly has advantages for engineering students; the danger of it is that the student, when he can calculate what he wants to calculate about his machines, will often never bother to find out the reasons for his methods; he will become a rule-of-thumb man instead of a scientifically trained engineer. The danger is a very real one, which must be combated if engineering students are to become useful in engineering development work, the work for which engineering colleges should strive to train their men. In spite of minor defects, the book may be recommended as a satisfactory text-book for students of electrical engineering in the early stages of their training.

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THIS little book is a reprint of articles published in the English Mechanic during the present year. The dry pile, built up in the same way as Volta's moist pile, was the invention of Jean André De Luc, who first described it in Nicholson's Journal, 1810. It was constructed by piling up in a glass tube a series of paper discs, coated on one side with silver leaf and on the other with thin leaves of zinc. A continual difference of potential was found to exist between the terminals. Modificacations were introduced by various workers,

notably Zamboni and Singer. The latter devised the form of apparatus now in the Clarendo Laboratory of the Oxford University Museum. This is arranged to ring a small bell, and s period of activity now extends to seventy-five years. Mr. Benham gives detailed instructions for setting up a dry pile of 2000 pairs, and describes a number of interesting experiments the may be carried out with its aid. The chief orig nal feature is the use of two ready-made coated papers in the construction of the pile. The work would have been of greater scientific value £ some quantitative results had been included. War Map of Italy and the Balkan States. 30 in × 40 in. (Edinburgh; J. Bartholomew and Co., n.d.) is. net in case, or 2s. 6d. on cloth

in case.

THIS map covers an area extending from Geneva in the west to Odessa and Asia Minor in the east. On the north it reaches Vienna, and takes in Malta on the south. Insets, on large scales, of the Dardanelles, Constantinople and its environs, and Trieste and its surroundings are provided. Each separate State is distinguished in colour, and railways are shown. The map, which may be highly recommended, can also be obtained on

rollers and varnished for 6s.

All About Zeppelins and other Enemy Aircraft. By F. Walker. Pp. 32. (London: Kegan Paul, Trench, Trübner and Co., Ltd., 1915.) Price 6d. net.

IT appears, from the preface, that "this little book is intended to explain fully, to a person of average intelligence, the nature and construction of enemy aircraft . . ." The author is a civil engineer, if one may so interpret the letters appearing after his name, but it is clear that his engineering training did not include an adequate course in aeronautics, or even freehand drawing, otherwise one might have been spared the many inaccuracies to be found in the book, and the stil more remarkable sketches (signed "F. W.") purporting to represent aircraft. Fig. 20, page 25, is said to show "a British biplane in flight." It is in reality a very poor sketch of the Wright biplane of 1908, to the under-carriage of which the artist has added a misrepresentation of four wheelbarrow wheels. A somewhat better sketch of a rear view of the same machine is introduced

in the following words: "Several of the Allies' biplanes have two propellers, as shown by the front view of a machine, Fig. 21."

Figs. 22 and 23 purport to be sketches of a "Taube" and an "Aviatik" respectively. Mr. Walker seems to have had misgivings, for he says: "But the details of these are so constantly changing, and the fact that they are utterly wrecked on reaching the earth, that we can only present the outward appearance in flight" (sic). It is difficult to believe that the delightful humour of these drawings, and of many of the statements in the book, is unintentional.

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FIG. 2.-Giraffe, from a tomb at Thebes. Middle dynastic. "Mediæval Ideas of the Elephant," by E. D. Cuming, in the Field for April 3 of this year.

One of the figures illustrating the latter article is here reproduced (Fig. 1), and we may also quote the following passage :

"About few animals did our ancestors weave more curious and fantastic legends than they built up round the elephant. This animal captured their imagination,

FIG. 3.-Giraffe, from an incised palette at Hierakonpolis. Early dynastic, Wilkinson's "Ancient Egyptians," vol. i. The second is from an incised slate palette found at Hierakonpolis, figured by Quibell in "Memoirs of the British Exploration Fund. The probable period to which it may be assigned is early dynastic, or roughly, circa 5000 B.C. G. R. EASTMAN. American Museum of Natural History.

The Magnetic Storm and Solar Disturbance of

June 17.

THE argument appears to me to drift again towards the old wrangle whether a particular solar disturbance has contributed to this or that particular magnetic storm. This is to me all the more surprising as for years past it has been urged that to connect the two phenomena in this direct way was to be deprecated and scientifically unsound; Fathers Cortie and Sidgreaves taking up a particularly uncompromising attitude in this respect.

I had the sun under telescopic as well as spectroscopic observation for many hours on twenty-seven out of the thirty days of last June, being prevented from doing so only on June 10, 23, and 29.

I submit that the mere telescopic appearance of a spot oubreak is not a safe index and criterion as to its activity, and consider that spectroscopic evidence should accompany ordinary direct visual observation. Now there was plenty of such evidence during the greater part of June, though spots were, at least at the beginning of the month, not very abundant. With June 12, however, things began rapidly to improve in this respect, a period of most intense activity being initiated by that most extraordinarily short-lived and superlatively active outbreak in abnormal low latitude (north) for the present phase of the activity period. The unprecedentedly rapid growth of this outbreak, which was really of an "explosive" intensity, was almost matched by an extraordinarily rapid decay, so much so that in spite of the magnitude the outbreak attained at its

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