OCTOB^ER 2, 1890] 



NATURE 



541 



■opposite name is believed to flow off in contrary direc- 

 tions in equal quantities from the surface of generation, 

 viz. the junction of the liquid with the positive plate," are 

 very crude even for amateurs. 



Mr. Urquhart's account of accumulators is a trifle 

 mixed. On p. 47, " the negative grids are filled with 

 litharge ; " but on p. 48 we have " the litharge (positive) 

 plate " ; the capacity of an accumulator with 32 lbs. of 

 plate is stated to be 50 ampere hours, whereas, as a 

 matter of fact, it is about two and a half times that 

 amount. The specific gravity of the solution, which 

 Mr. Urquhart says should be i "220 when the cell is fully 

 charged, falls, he says, about o'l for every 5 ampere 

 hours, no reference whatever being made to the size of 

 the cell. The specific gravity, then, of the liquid of an 

 accumulator from which 61 amperes could be taken, 

 would fall to nought at the end of the first hour of dis- 

 charge, though what that might mean we do not know. 

 On p. 51 we are told in connection with the miner's lamp, 

 that an accumulator weighing only 3 lbs. can " be made 

 to light a small incandescent lamp for ten or twelve 

 hours, yielding a light of two or three candles." Now 3 

 candles for 10 hours means about 120 watt hours, so that, 

 if we assume that the box and liquid weigh together only 

 8 ounces, this marvellous accumulator stores something 

 like 140,000 foot-pounds of energy per i pound of plate. 

 On p. 294 the weight of the miner's accumulator and 

 incandescent has gone up to 7 lbs., and the light has 

 ^one down to i or ij candle. 



' This sort of looseness runs through the book, "The 

 legal ohm i? the resistance presented by a column of pure 

 mercury, 106 centimetres in length and i millimetre in 

 iSection," the word square before millimetre, and all 

 I'eference to temperature being omitted. After the defini- 

 tion of the watt it is stated that " An incandescent lamp 

 is said to need 4 watts per candle power, or 60 watts in 

 all to run it ; " " said to need " looks as if it were a defini- 

 tion instead of being an experimental fact, and since the 

 candle power of the 60 watt lamp is not mentioned, it 

 might appear that all incandescent lamps from 2 to 2000 

 candles power required 60 watts. In speaking of the 

 number of lamps a dynamo can maintain glowing, the 

 author says, " More lamps could be maintained at 5 watts 

 per candle than at 4 ; " we should very much like to know 

 why. The phase of an alternate current is defined as its 

 life. Under " Cost of Electric Light " we are told, " The 

 Board of Trade unit, consisting of a kilowatt (a thousand 

 watts for one hour) is the recognized standard of calcula- 

 tion," and that this is not a printer's error is shown by 

 the author going on to say, " that a kilowatt can be sold 

 at a fair profit at from ^d. to 9^." Perhaps the author 

 will favour us with the market value of one mile an 

 hour. 



A large amount of useful information has been collected 

 together, the illustrations are abundant and well executed, 

 and probably much time has been spent in the compiling 

 of this book. Is it not a pity then that its value, both for 

 the technical reader and for the electrically-lighted house- 

 holder, should be much diminished by the unscientific 

 vagueness that runs through it, and by the indis- 

 criminate mixture of th/£ aptiqu? with, the modern in 

 <ts -pages ? ; 



■ ' NO. 1092, VOL. 42] 



COUES'S ''HAND-BOOK OF ORNITHOLOGY: 



Hand-book of Field and General Ornithology : a Manual 

 of the Structure and Classification of Birds. With 

 Instructions for Collecting and Preserving Specimens. 

 By Prof. Elliott Coues, M.A., M.D., &c. Pp. 344. 

 (London : Macmillan and Co., 1890.) 



N' ATURALISTS are not unfrequently regarded as be- 

 longing to two categories— those of " the field " and 

 those of "the cabinet." The "field naturalist" is too 

 often little acquainted with scientific method, and apt to 

 undervalue scientific research. On the other hand, the 

 " cabinet naturalist " in many cases despises the labour of 

 his brother of " the field," and thinks that he can solve all 

 the problems of life without studying the living organisms. 

 The best naturalists — it is not necessary to quote names 

 in support of such a truism — have always been those who 

 combine much experience in the field with great study in 

 the cabinet. The author of the present work is well 

 known to possess both these qualifications, without which, 

 indeed, he could hardly have ventured on the task of 

 writing it. His experience in the field, as he tells us in 

 his prefatory remarks, reaches in time over thirty years, 

 and extends in area over large portions of North America. 

 Having made personal acquaintance with most of the 

 species of North American birds, and having shot and 

 skinned with his own hands several thousand specimens, 

 he may reasonably claim to speak with authority on field 

 ornithology. On the other hand. Dr. Coues is the author 

 of the " Key to .North American Birds," which has passed 

 through many editions, and is generally recognized as the 

 standard text-book of the American ornithologist. On 

 this branch of his subject, therefore. Dr. Coues is likiJwise 

 entitled to claim our full attention. ■ ' . 



Dr. Coues commences his hand-book with " Field Orni- 

 thology," which, as he truly says, should lead the way to 

 ^ystematism and description, and devotes nearly ninety 

 pages to this part of his work. The necessary implements 

 for collecting, the various instruments and materials 

 required for making skins, the proper modes of registra- 

 tion and labelling, and the right way to keep a collection 

 when made, are all discussed in turn, and admirably ex- 

 plained and illustrated. " Labelling," we are glad to see, 

 Dr. Coues expatiates upon at full length, and it is im- 

 possible to exaggerate its importance. How often are 

 the best prepared and rarest specimens of natural objects 

 rendered comparatively useless by the neglect of this 

 requirement ! We do not presume to say that all the 

 twelve particulars insisted upon by our author should be 

 given in every case, but the locality, the date, and the 

 collector's name should at least never be omitted from the 

 label of a scientific specimen. 



A still more important part of Dr. Coues's hand-book is 

 that of " General Ornithology," which occupies the re- 

 mainder of the present volume. It is divided into four 

 sections. In the first of these the author endeavours to 

 define exactly what a bird is, and discusses the position 

 of the class "Aves" in the series of Vertebrata..' In the 

 second section the principles of classification are reviewed, 

 and it is shown that morphology or bodily structure is the 

 only safe guide to a natural system. The third section is 

 devoted to a description of the external chafadters of 



