igb 



NA TURE 



[July 28, 1904 



amount of material to be dealt with makes compres- 

 sion a sine qua non. It is only a taste we get; but 

 the voluminous references to original sources forming 

 the extensive footnotes point the way to a fuller feast. 

 It is as a reference book that the chief value of the 

 volume will be found ; it is not intended for consecu- 

 tive reading. 



Each paragraph is a highly condensed account of a 

 particular part of the subject. Thus von Rohr con- 

 centrates into a few pages the principal facts treated 

 at more adequate length in his treatise on photo- 

 graphic objectives. 



Again, von Seidel's method for dealing with the 

 aberrations of lenses is limited to what seems very 

 scanty treatment when the importance of the method 

 is taken into consideration. But for fuller information 

 the author is obliged to refer to a forthcoming work 

 by A. Konig and himself — there is only room for 

 outlines in a work like the present. 



The work throughout is produced with the 

 thoroughness which is characteristic of German 

 publications. We look forward to the completion of 

 the entire book. 



Laboratory Exercises in Physical Chemistry. By 

 Frederick H. Getman. Pp. viii + 241. (New York: 

 Wiley and Sons; London : Chapman and Hall, Ltd. 

 1904.) Price 8.S. 6d. net. 

 The title of this book might lead one to expect that 

 what is really a distinct want had at length been 

 met. Beyond the title, however, there is little in it 

 that merits favourable comment; both in conception 

 and in execution it is most inadequate. One finds, 

 for example, that viscosity and surface-tension are 

 accorded fourteen pages, of which four are purely 

 theoretical and wholly out of place, whilst solubility is 

 disposed of in four and a half pages. Again, we dis- 

 cover molecular volume in the chapter on thermometry 

 and polanmetry in the chapter entitled " The Spectro- 

 scope " ! Not only is the author hopelessly deficient 

 in the general sense of proportion and arrangement, 

 but in matters of detail he is equally at fault. He 

 actually (p. 30) introduces the temperature correction 

 of the barometer into the calculation of a vapour 

 density by Victor Meyer's method— the only method 

 given— and does not even succeed in doing it cor- 

 rectly. He defines the unit of resistance as the inter- 

 national ohm (p. 153), and then gives his data in terms 

 ot the J>iemens mercury unit (p. 172), which is never 

 dehned or even mentioned. Turning to his practical 

 instructions we encounter the same thoughtlessness 

 and omission of important details. The student who 

 carried out a series of conductivitv measurements at 

 diHerent dilutions according to the instructions on 

 p. 177. tor example, would obtain truly wonderful 

 results, tor no mention is made of the necessity of 

 having two pipettes so adjusted that one withdraws 

 exactly the same volume as the other delivers. What 

 again is a student to make of the instruction on 

 ''■^•'^ ,.'^''°".^"° "■''■ °f ^ N/32 solution of pure 

 sodium hydroxide is titrated with the dry acid of 



suffice """"'"'^ '" '°""''' "' "^''^"^ instances 



In closing the volume one can onlv express the hope 

 that there may speedily be forthcom'ing a book which 

 shall be in fact what this is in pretension. 

 LesAni.nat,^ domestiques. Bv J. .\nglais. Pp. 103 • 



illustrated. (Paris : Schleicher Freres et Cie.; 1004 

 liiE object of this volume mav be best described by 

 paraphrasing the first portion of the introduction, 

 where Dr Anglais states that it has been his aim, with 

 the aid of a number of ingeniouslv planned coloured ' 

 plates, to describe the essential characteristics, both 

 external and internal, of a certain limited number of | 



types of our most familiar domesticated animals. It 

 is addressed to all who desire to make themselves 

 acquainted with the leading features and characteristics 

 of such animals, without the drudgery of long and 

 profound practical study, and to acquire a general idea 

 of their physiology and the history and object of their 

 subjugation by man. As many details as possible of 

 the peculiarities of the external form and of the internal 

 anatomy are displayed in the illustrations and de- 

 scribed in the text, so that it is hoped the work will 

 serve in the case of some readers as an epitome of 

 comparative anatomy and morphology, while for 

 others it may form a starting point for more detailed 

 study. The animals selected for illustration are the 

 horse, the cow, the sheep, the pig, the dog, the cock, 

 and the goose, each being illustrated and described 

 on the same plan. 



The illustrations of each species are five in number, 

 and are printed on both sides of the cards, which are 

 cut out to the shape of the animal, and so arranged 

 as to fold over one another. The first shows the 

 external form, the second the skeleton, the third the 

 vascular system, the fourth the muscles, and the fifth 

 the nervous system and viscera. 



So far as anatomy can be learnt by means of 

 diagrams, the work appears to deserve all that is 

 claimed for it, and it will probably prove of consider- 

 able assistance to artists. Whether all the subjects 

 selected for illustration would meet with commend- 

 ation at the hands of breeders may, perhaps, be open 

 to question. R. L. 



NO. 18 I 3, VOL. 70] 



LETTERS TO THE EDITOR. 



The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for Itiis or any other part of Nature. 

 No notice is taken of anonymous iiimniunicaiions.l 



Traction of Carriages. 

 In tentative answer to your correspondent, p. 270, I 

 suggest the following : — 



The best angle of traction on a rough or irregular surface 

 is at an upward inclination to its general slope. This » 



upward slanting pull can be applied to a two-wheeled 

 vehicle, and to the fore-wheels of any vehicle, but not to 

 the hind wheels — especially if they are far away. 



Consider, further, the summit of a hill, and let a waggon 

 be so elongated that its hind wheels are still ascending 

 while the horse is descending : his pull is exerted at a very 

 bad angle on this part of the load, and in extreme cases 

 Ihe hill might almost act as a detent. 



I should like to take the opportunity of saying that 

 whether the traditional heavy draught of a long-bodied 

 carriage is well founded or not, I am convinced that the 

 ordinary hanson cab is badly balanced, and that a horse 

 would be better with some load on his bacic, except when 

 descending a hill. The comfort of a wheelbarrow over a 

 balanced cart is considerable. 



Though it may be easy to overdo the loading, nothing 

 can be worse than a constant upward pressure on the chest 

 of a horse : a pressure which at present automatically in- 

 creases on an up grade, thus tending to deprive the animal 

 of part of his own weight, on the e.xistence of which the 

 efficacy of every locomotive depends. 



Oliver Lodge. 



Lobster Hatching. 



Perhaps your readers interested in economic marine 

 biology may care to know, as a small contribution to the 

 record of times and seasons, that the berried-lobsters kept 

 at the Port Erin Biological Station started hatching out 

 their young on July 15. So far the loss after hatching has 

 been under i per cent. We find the best food for the young 

 lobsters to be finely teased up fresh liver of the common 

 shore crabs. W. A. Herdmak. 



Biological Station, Port Erin, Isle of Man, July 22. 



