512 



NATURE 



[February 15, 191 2 



which was formerly |>l;ni(l .iimui^ the Chi-ili'-tMin.ii;i. 

 Dr. Annandale confirms JuH'unV sialiim m that it 

 belongs to the Ctenostonia!;i, aiul Xv slmus i!i.it it is 

 cl(i'~flv rclalcd to Arachnoidea, wh'uli \\.i> ai our limi- 

 oiti (I a^ < Aidcnro for the mariiir uiij^in of iln- tauiia 

 of 1 -al^i- 'l'ant;an\ ika. 



.\ miinhcr of misprints liavc escaped (iMiniinn. On 

 p. ni llir words "co-type" and ■ |)aral\ |if " sci-iii l<i 

 have clumj^ed places, willi tiie disasiKni-- i' suit that 

 we are left in doubt as to the sense in which these 

 terms are used throughout the volume. In the sen- 

 tence, "Some of these species . . . are identical wiili 

 others . . . closely related to European forms " 

 (p. 12), "and" preceded by a comma should appar- 

 ently be inserted after " with." On p. 177 it is stated 

 that Kraepelin's classification of the Polyzoa is "less 

 liable to criticism than that followed by Braem," 

 where the context appears to imply that it is more 

 so. It is not clear in what way the " force of gravity " 

 can account for the mutual attraction of gemmules 

 floating on the surface of water (p. 118). 



THE PHYSICS OF ELECTRIC LAMPS. 

 Dcr clektrische Lichtbogen: Expcr'nui'tilahu^rtrag auj 



Wunsch des wissenschaftlicheii Vcreins cu Berlin 



i^tlialtcii am 11 Januar, 191 1. By Prof. H. Th. 



Simon. Pp. iv + 52. (Leipzig: S. Hirzel, 1911.) 



Price 2 marks. 

 Les Lampes Electriques. By Prof. H. Pecheux. 



Pp. 186. (Paris : Gauthier-Villars, n.d.) 



PROF SIMON'S monograph is a reprint of a lec- 

 ture delivered in Berlin, and gives in an in- 

 teresting and consecutive form a brief summary of the 

 principal physical aspects of the electric arc. The 

 numerous physical phenomena presented by the arc 

 have long afforded a most interesting field for research, 

 and it is remarkable into how many bypaths these 

 researches have led. Although the arc in its practical 

 application is primarily a source of light, the most 

 eflficient which we possess, and secondarily a source 

 of heat, neither of these aspects receives more than 

 a very brief mention in the pamphlet before us. 



It is indeed somewhat remarkable that so little 

 attention has been given by physicists to the problem 

 of the emission of light by the flame arc, a field of 

 research which would seem to be of great theoretical 

 and practical value. But for some reason or other 

 the electrical characteristics of the arc have alwavs 

 appealed more to investigators, and these liave been 

 explored far more thoroughly, with valuable and in- 

 teresting results. Notably the investigations of Prof. 

 Simon himself on the telephonic arc and of Duddell 

 on the musical arc may be referred to ; these have led 

 to the use of the arc as a source of sustained oscillation 

 for the transmission of wireless signals, a direction 

 in which its utility could scarcely have been foreseen. 



These phenomena and their theoretical explanation 

 will be found clearly described in Prof. Simon's little 

 book, which, if it does not attempt to add much to 

 our existing knowledge, summarises it well. In 

 addition to a number of diagrams the book is illus- 

 trated by a coloured reproduction of an autochrome 

 photograph of a flame arc, which is fairly successful 

 NO. 2207, VOL. 88] 



idiisldiiin^ th.- diriiculty of the subject. The genera; 

 tdicct, howcvfi , i- far too red. 



M. Pecheux '^ liii!'- book forms < volume* 



of till' " I"-rn\i lope (lii- Scicntifique dcs Aidc-Mtl'moire,' 

 and is a hrirf and m H-written description of th* 

 various types of eUctric lainj) in use. A good deal o 

 s|,a(. is devoted to the sul)j'( t of the electrical char- 

 aciiiisiii-, a suljji'Ct which always s.cnis attractive 

 to writers un incandrsccnt lamps, and has re- 

 ceived somewhat more att< niic^n than its importanc* 

 warrants. On the other hand, the amount of atten- 

 tion i;ivon to the light-emitting projjerties and efficiencj 

 is perhaps somewhat meagre. M. S. 



OUR BOQR, SHELF. 



Farm and (rorden Rule-book: a Matiual of Rcr"i^ 

 I\'hIcs and Reference. With Recipes, Preci 

 !• urmula:i, and Tabular Information for the L/ic , 

 General Farmers, Gardeners, Fruit-growers, Stock I 

 men. Dairymen, Poultrymen, Foresters. Rura 

 Teachers, and others in tJic J'nited St: 

 Canada. By L. H. Bailey. Pp. xxv + 5.'s7 

 York : The Macmillan Company ; London : Mao 

 millan and Co., Ltd., 191 1.) Price Ss. 6d. net. 

 This book affords a striking commentary on th< 

 progress of agriculture and horticulture in thest 

 latter days ; whereas a generation ago the cultivatot 

 could carry all his rules and recipes in his head, h» 

 now finds such a bewildering number of possibilitie; 

 open to him that, without the help of some sue! 

 volume as this, he will be wholly unable to make an^ 

 use of the stores of knowledge accumulated a 

 numerous experiment stations throughout the world. 

 The first section shows how to use the weathe 

 map and to interpret as far as may be the weathe 

 indications ; then follow directions for making observa 

 tions and using them. Next comes an account o 

 the soil, the elements of which it is composed, wate 

 statistics, and so on, and finally rules to be followe< 

 in order that fertility may be maintained. Consider 

 able space is devoted to chemical fertilisers, as th< 

 importance of the subject warrants ; in particular th' 

 farmer is shown how to calculate the fair value of j 

 manure from its guaranteed composition, and hov 

 to convert one form of guarantee into another 

 Typical mixtures of manures for various crops an 

 suggested, the range in both cases being wide, so a 

 to ensure that the tables shall have as large a valu' 

 as possible. Dates for sowing, planting, and pro 

 pagating various plants in the different regions ar 

 given, followed by tables showing the number o 

 plants that should go to one acre and also the distano 

 apart at which the plants must be set. Several page 

 are devoted to the yields of field crops in the differen 

 States, wherein some very interesting and suggestiv- 

 data occur. The best vield is commonly double am 

 sometimes three times the average for a particula 

 State, a fact which shows that there is still room fo 

 much levelling up in the farming efficiency of th 

 cultivators, even when allowance has been made fo 

 the fact that some of the high yields are partly du- 

 to exceptional climatic conditions. 



Then we get into fruit and greenhouse figures, am 

 find tables containing such uninteresting but valuabi 

 I data as the legal size of apple barrels in variou 

 I States, standard dimensions of flower pots, recipe 

 I for painting hot-water pipes, making liquid puttv fo 

 glazing, &c. This section ends up with a list, eight 

 j pages long, of fungus and insect pests the growe 

 j may reasonably expect, together with a few shor 

 I hints showing how each pest may be more or les^ 

 j controlled. 



