Jllv 14, 1910J 



NATURE 



39 



plates, there are 215 figures in the text, all of which 

 appear to have been specially drawn for the book, and 

 many are quite original. The coloured figures are 

 reproduced bv the three-colour process, and are on 

 the whole satisfactory, though one or two are scarcely 

 recognisable. The text-figures include line-drawings 

 of the forms of crystals, and excellent half-tones repre- 

 senting actual crystals and mineral specimens. 



To the English student of mineralogy such a book 

 might be used with advantage as a German reading 

 book. The sentences are short and not involved. 



.4 Syiiojysis of the Orthoptcra of Western Europe. 

 By Dr. Malcolm Burr. Pp. 160. (London : Oliver 

 Janson, 1910.) Price 35. 



The present work appeared in instalments from 1903 

 to 1909 in the Entomologist's Record, and in its present 

 form will be extremely useful as an introduction to the 

 subject, and as a tourist's guide, especially as its small 

 size renders it more convenient than Brunner von 

 Wattenwyl's work on European Orthoptera, or that 

 of Tiimpel's on those of Central Europe. Dr. Burr's 

 work includes all the countries west of (and includ- 

 ing) the neighbourhood of \'ienna. For eastern 

 Europe we have (for those who can use it) the great 

 Russian expansion of Tiimpel's book by Jacobsen and 

 Bianchi, which includes all the Orthoptera of central 

 and eastern Europe, and Palajarctic Asia. 



Dr. Burr has given short but careful descriptions 

 of genera and species, and also tables of species under 

 the genera, and he has very properly included the more 

 important naturalised species, such as Periplaneia 

 australasiae. Orthoptera are, however, very liable !o 

 be carried about from one place to another, and mere 

 casual visitors are verv properly only mentioned by 

 name, as on po. 17, 18. &c. A long-legged Japanese 

 grasshopper, Dicsirammena marmorata, not men- 

 tioned by Dr. Burr, has several times been captured 

 recently in London. 



Prehistoric Man. By Joseph McCabe. Pp. viii-f-i^S. 



(London : Milner and Co., Ltd., n.d.) Price is. 



net. 

 This book gives an excellent popular exposition of 

 the present state of our knowledge of prehistoric 

 anthropology. The chapters on Palaeolithic man and 

 his implements are full of interest. Within the last 

 few years a considerable number of more or less com- 

 plete Palaeolithic skeletons have been discovered in 

 France and elsewhere, and great additions have been 

 made to our knowledge of man in this distant epoch. 

 In this little volume will be found a lucid description 

 of the latest discoveries. The author is not content 

 to give a mere list of more or less disconnected data, 

 but always endeavours to weave his material into a 

 continuous evolutionary story. This tendency, though 

 admirable in a popular writer, appears in some cases 

 to lead to a slight distortion of the facts in order to 

 make them fit into the theory. For example, the 

 Palaeolithic race represented by the Grimaldi, Galley- 

 hill, and other remains is assigned to the later 

 Palaeolithic, though the geological evidence appears to 

 be pretty clear that these remains belong at least to 

 the middle Palaeolithic. The Gibraltar skull has re- 

 cently been shown by Dr. Keith to have been the first 

 Palaeolithic skull found (1843) in Europe, and to re- 

 present one of the most primitive races. This dis- 

 covery does not appear to have been known to the 

 author. 



The chapters on the Neolithic and Bronze ages show 

 that our knowledge of these periods is still in a very 

 unsatisfactory condition, but that is not, of course, 

 the fault of the author of this w-ork. 



(i) Metallografia appUcata ai Prodotti Sidcriirgici. By 

 I'mberto Savoia. Pp. xvi-i-205. (Milan: U. 

 Hoepli, 1909.) Price 3.50 lire. 



(2) Lo Zinco. By Prof. R. Musu-Boy. Pp. xiv-l-219. 

 (Milan : U. Hoepli, 1909.) Price 3.50 lire. 



Both these little treatises belong to the excellent series 

 of " Manuali Hoepli," and, like other members of the 

 series, are written by specialists in their respective 

 subjects. They possess the merit, common to prac- 

 tically all other works of this series, of imparting in 

 the fewest possible words the most essential facts and 

 principles. The treatise on the metallopraphy of iron 

 is essentially a practical guide for the laboratory 

 worker. Its author was sent from Italy to study the 

 methods adopted in the laboratories of Le Chatelier, 

 Fremont, and Guillet, and on returning home estab- 

 lished the metallographical laboratory of the Milan 

 steel works. The author has selected for description 

 the methods he has found best suited in practice, and 

 has illustrated the work by nearly 100 of his own 

 microphotographs of steel in its different states. 



The treatise on zinc is of a more general character, 

 and calls for little coinment. It deals with the ores, 

 methods of extraction, history, statistics, and uses of 

 the metal. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to returni 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.] 



Ooze and Irrigation. 



May I be allowed to reply to some inquiries? 



(1) It is thought by some that my remarks applied 

 especially to foreign lands. Let me point out that the ooze 

 of our English rivers is often just as fertile as that of the 

 Nile, and that the number ot annelids found in the ooze 

 is enormous. This may be illustrated by reference to the 

 Thames. The late Frank Buckland tells us that when he 

 kept fish he " fed them with red worms collected from 

 the Thames mud. These worms cost 4s. 6d. a quart ; the 

 price of Thames worms, like everything else, has increased 

 considerably." Now whether these worms were true 

 annelids, or merely the larvae of insects, the point is the 

 same. In the case of Tubifex and its allies, a quart would 

 mean many hundreds of thousands. Mr. Shrubsole, 

 myself, and others, have frequently examined the ooze 

 from various parts of the Thames, and the number of 

 different species of mud-frequenting worms is very great, 

 while it is utterly impossible to estimate the total of 

 individuals. 



(2) .'Vnother interesting point is continually coming under 

 my observation. When a number of annelids taken from 

 the ooze is examined, it is found that the tail, which is in 

 constant rhythmical motion in the water, is festooned with 

 numbers of symbiotic vorticels. These move to and fro in 

 the water, and are constantly capturing the bacteria and 

 other lowly forms of life with which the putrid water is 

 laden. So far as I am aware, no biologist has ever given 

 this fact, or the action of the vorticels, any detailed study 

 with a view to ascertaining their action, and their relation 

 to their host on the one hand, and the water and soil on 

 the other. 



(3) It would be of great value to science if someone would 

 carefully examine the ooze before and after passing through 

 the bodies of annelids, and ascertain what is the nature 

 of the change that has taken place. Is there any difference 

 between the quantity of nitrogen in pure mud and that 

 which has been digested? 



These and many other problems having a vital bearing 

 on agriculture need attention, and it is to be hoped that 



NO. 2124, VOL. 84] 



