November 23, 191 1] 



NATURE 



107 



(i) The bacteriology treats of bacteriological 

 (methods, pathogenic bacteriology, and bacteriology 

 as applied in hygiene in the examination of water, 

 milk, foods, disinfectants, &c. A few slips need cor- 

 recting — e.g. the statement that an antibody consists 

 of two parts (p. 19)— and the Wassermann reaction 

 ^needs amplifying somewhat ; otherwise there is little 

 |to criticise, and some portions of the book are par- 

 jticularly good, e.g. the section on disinfectants. 

 '1 (2) The pathology suffers somewhat from the 

 ,^ttempt to include everything in so small a book — e.g. 

 diseases of the teeth and parasitic worms — and other 

 more important and fundamental processes are in 

 jionsequence too briefly discussed. Fatty infiltration 

 ,knd degeneration are treated as though they are quite 

 distinct. It is stated that active immunity is con- 

 iferred by the injection of an anti-serum, whereas it 

 jis correctly stated a couple of lines later that this 

 procedure confers a passive immunity. The diagrams 

 ^indicating the interaction that occurs in the Wasser- 

 mann reaction should render this subject clear. 



R. T. H. 



,'ienior Chemistry. By Dr. G. H. Bailey and H. W. 

 Bausor. Pp. viii + 5og. Price 45. 6d. 



Senior Magnetism and Electricity. By Drs. R. H. 



! Jude and J. Satterly. Pp. viii + 446. Price 55. 



'Senior Heat. By Drs. R. VV. Stewart and J. Satterly. 

 • Pp. viii + 300. Price 3^. 



'(London : W. B. Clive, University Tutorial Press, 

 [f Ltd., 1911.) 



All these books are based upon previous volumes 

 .ssued by the same publishers. The first is an adapta- 

 :ion apparently of Dr. Bailey's "Chemistry for 

 Matriculation," which was reviewed in our issue of 

 (May II, 19 II (vol. Ixxxvi., p. 345); the second of Dr. 

 fude's "Matriculation Magnetism and Electricity," 

 loticed in these columns on June 23, 1910 (vol. Ixxxiii., 



pD. 485), and the third of the late Dr. Stewart's book 



I on heat, noticed at the same time as the volume on 



^^■nagnetism and electricity referred to. 



: It would seem that the present volumes cover those 



5arts of the respective subjects included in the sylla- 



ui<;es for candidates presenting themselves at the 



•or Local Examinations conducted by the Univer- 



of Cambridge. 



■ Useful Metric Equivalent Tables. (London : 

 ic Central Translations Institute, n.d.) Price 6^ 



I-. 



,'k'ovisiON is made in these tables for the range of 



tquivalents likely to arise in commercial dealings be- 



'1 this country and others using the metric system. 



calculations are based upon figures supplied by 



i?oard of Trade. The price equivalents deal with 



yards, square feet, square yards, cubic feet, 



,-lons, pounds avoirdupois, hundredweights, and 



jOrty cubic feet measurements— which are useful for 



ii'Hving freight charges. The prices are calculated 



le rate of exchange of 25.22 francs to the £. 



landbonk of Physics and Chemistry. By H. E. 

 rbin and A. M. Stewart. Pp. viii + sig. Fourth 

 ition. (London: J. and A. Churchill, 1911.) 

 icQ 7^, 6d. net. 



first edition of this book was reviewed in Nature 

 inuary 4, 1900 (vol. Ixi., p. 221). It will suffice 

 IV that in Its present form the volume covers the 

 nded syllabus of work required for the first 

 iination of the Conjoint Examining Board of the 

 il Colleges of Physicians and Surgeons. Addi- 

 11 articles have been introduced in the present 

 >n on hydrostatics, the polarisation of light, and 

 tgen rays. 



NO. 2195, VOL. 88"! 



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 this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Electricity and Vegetation. 



Without pretending to answer the question raised by 

 Mr. Benham at the conclusion of his letter on p. 41 of 

 Nature of November 9, and without prejudging the results 

 of recent experience on electrification of crops as reported 

 on by Dr. Priestley and other impartial investigators, I 

 would remind him and your readers generally that it is 

 unsafe to attach a positive conclusion to a negative result 

 obtained by supposed electrification of a wire network over 

 a field, unless there is reasonable guarantee that such 

 network was really kept positively electrified during con- 

 siderable periods. 



For instance, it has been attempted in the past, and it is 

 still tempting, to supply electricity to a network by means 

 of elevated spikes, arranged so as to utilise the gradient of 

 potential naturally existing in the atmosphere. But thinic 

 what singularly perfect insulation would be required to 

 enable electricity slowly supplied in this way to accumulate 

 until a fizzing point was reached. The attainment of such 

 potential over a large area would in this climate be quite 

 impracticable except when a thundercloud was passing 

 overhead. 



The same difficulty of adequate insulation must have 

 militated against many attempts made in the past to supply 

 electricity from artificial but old-fashioned high-potential 

 sources, especially when the area to be supplied extended 

 over many acres. 



It must be further remembered that any metallic network 

 not really charged, but kept practically at zero potential by 

 leakage to earth, would be presumably detrimental to the 

 growth of plants beneath it ; inasmuch as it would tend to 

 screen them from the natural inductive electrification to 

 which they are entitled. Oliver Lodge. 



Fish and Drought. 



The summer of the year 1911 will long be remembered 

 for its excessive heat and dryness. These were especially 

 trying to the inhabitants of streams and shallow lakes or 

 ponds. I had the opportunity of studying a remarkable 

 instance of this, which I think is worth recording. 



The Chateau of Marchais, with its magnificent domain, 

 the property of the Prince of Monaco, lies about 16 kilo- 

 metres east of Laon, in the department of Aisne, and is well 

 known as one of the best shooting estates in France. The 

 sketch (Fig. i) represents the park. It occupies a rectangle 

 surrounded by a ditch or moat. A, B, C, D, consisting of 

 four canals, each 1250 metres long and 16 metres wide, and 

 carrying usually a depth of I3 metres of water. These 

 canals form a continuous sheet of water, 5 kilometres long, 

 and there is a bridge, a, b, c, d, over each of them. The 

 country, though well-wooded, is flat and peaty, and the 

 level of the water in the ditch is that of the water in the 

 ground all round it. Like the ground-water, it is subject 

 to rise and fall according to the wetness or dryness of the 

 season. 



When I arrived on the morning of September 29, I 

 observed that the ditch was quite dry, with the exception of 

 the small tank or enclosure (/) for ducks at the lodge known 

 as the Porte Rouge, where entry to the park is obtained 

 over the bridge marked (b). Yet the water of the ditch is 

 always full of fish, principally carp, tench, perch, and pike. 

 Now there was nothing but dry mud. With the water the 

 fish had entirely disappeared, and without leaving a single 

 dead one to mark luherc they had before abounded. 



On the evening of September 29 a violent storm of wind 

 and rain broke, and it raged over the whole of northern 

 Europe until October i. I was curious to sc? the effect 

 which this first important rain, which marked the breaking 

 of the drought, would have on the ditch. 



It is right to say that the full significance of the dryness 

 of the ditch and the absence of dead fish had not suffi- 

 ciently impressed me. I only felt that I was witnessing • 



