December 8, 1904] 



NA TURE 



123 



Taking the book as a whole, the reader's interest 

 is fully sustained, and although one finds instances of 

 duplication of cautions, this is evidently the result of 

 the sectional arrangement and so unavoidable. 



In so excellent a work detailed criticism is a some- 

 what thankless task, but it might be suggested that 

 in discussing the risks attendant on the use of 

 petroleum lamps, some notice might be taken of the 

 views of Sir James Dewar, Dr. Boverton Redwood, 

 and the late Sir Frederick Abel, as to increase of the 

 flash point not being so complete a solution of the 

 trouble as the author leads one to believe. 



It might be well to note in a future edition that 

 barium peroxide, which on p. 117 is said to become 

 dangerous at 800° C, may also give rise to fire at 

 atmospheric temperatures when exposed to friction 

 with organic matter. 



On p. 187 it is stated that one pound of calcium 

 carbide furnishes 4 to 42 cubic feet of acetylene, which 

 is perfectly true of the inferior carbide made on the 

 Continent, but with material of the quality until 

 recently made at Foyers the yield rarely fell below 

 5 cubic feet per pound. 



Occasionally one finds slight discrepancies in the 

 statement of temperatures in different parts of the 

 book, the temperature at which lead fuses being given 

 at p. 291 as 325° C, whilst in the appendix, 

 p. 343, it is stated to be 334° C. Such details as these, 

 however, detract but little from the value of a book 

 which is an important and most valuable addition to 

 the technical literature of the day. 



THE DETERMINATION OF MINERALS. 

 Mineral Tables — for the Identification of Minerals hy 

 their Physical Properties. By Arthur S. Eakle, 

 Ph.D. Pp. 73. (New York : John Wiley and Sons ; 

 London : Chapman and Hall, Ltd., 1904.) Price 

 5s. 6d. net. 



STUDENTS of mineralogy, miners, prospectors, 

 and others interested in the determination of 

 minerals by methods which do not involve the use of 

 elaborate apparatus, will find this little book a useful 

 addition to the literature of the subject. 



The tables, though forming a volume of only 73 

 pages, include nearly 250 minerals, comprising all 

 the commonly occurring ores, veinstones, and rock- 

 formers, as well as a few species of more restricted 

 occurrence. They are designed for the identification 

 of unknown minerals by the examination of their 

 physical properties alone; blowpipe reactions are not 

 employed at all in the scheme. It is claimed by the 

 author that the determination of minerals by blow- 

 pipe analysis is less apt to become merely mechanical 

 if it has been preceded by practice in identification by 

 physical properties. This is no doubt true ; and if, as 

 is often the case, the beginner is tempted to rely upon 

 blowpipe analysis alone, that intimate acquaintance 

 with minerals which is only gained as the result of 

 the systematic observation of their physical properties, 

 and which is so valuable for their ready recognition 

 in the field, is either missed entirely or is only very 

 imperfectly acquired. Indeed, in most cases blowpipe 

 NO. 1832, VOL. 71I 



reactions are best employed by the determinative 

 mineralogist in confirming conclusions already arrived 

 at from the evidence of physical properties. They are, 

 however, so invaluable for this purpose, and afford 

 such an indispensable aid to identification by physical 

 properties, that any determinative scheme from which 

 they are entirely excluded must be in a sense deficient. 

 The author would have greatly added to the value of 

 the tables by including for each species a brief state- 

 ment of its distinctive blowpipe reactions, and we 

 venture to suggest this extension of the scope of the 

 work to him for future editions. 



As in all tables of this kind, the identification of an 

 unknown mineral is effected by a process of elimin- 

 ation. The minerals dealt with in the book are first 

 divided into categories according to their colour in the 

 powdered condition; these groups are then subdivided 

 into minor groups according to the colour of the 

 mineral in mass; and finally, the species in each of 

 these divisions are arranged in order of hardness. 



In general plan the tables are similar to those of 

 VVeisbach; but they differ from them in certain re- 

 spects, notably in their greater simplicity, and in the 

 abandonment of that indefinite and unsatisfactory 

 property lustre, as an important means of discrimin- 

 ation. The tables are preceded by an " analytical 

 key," by reference to which it is possible, after pre- 

 liminary observations of streak and colour, to see at 

 a glance in which table the mineral under examination 

 will be found; it is then only necessary to determine 

 the hardness and one or two other characters, such as 

 crystalline form, structure, cleavage, specific gravity, 

 and so forth— all of which are described in columnar 

 form in the tables— to complete the identification. 



The omission of the great majority of those rare 

 mmerals which the ordinary student or prospector is 

 scarcely likely to meet with, and which by their inser- 

 tion render so many books of this kind dear and un- 

 necessarily complicated, is to be commended The 

 tables are certainly to be regarded as among the most 

 satisfactory that have yet appeared. 



OUR BOOK SHELF. 



Die Sinnesorgane der Pflanzen. By G. Haberlandt. 

 T„,?",^..; p!P^'&,= .Barth, 1904.) Price I mark. 

 IHis little book which is appropriately dedicated to 

 he memory of Darwin, was given as a lecture before 

 the recent Versammlung deutscher Naturforscher und 

 Aertzte at Breslau. The author devotes the chief part 

 01 his space to a semi-popular account of the various 

 types of structures, such as bristles, hairs, papilla 

 which serve for the perception of mechanical stimulus' 

 1 his is necessarily, to a large extent, a recapitulation 

 01 his own interesting work on the subject, and is 

 tollowed by an account of the statolith theory— the 

 hypothesis independently put forward by himself and 

 Nemec as explaining the sensitiveness of plants to the 

 force of gravity. The most interesting part of the 

 lecture is, however, Haberlandt's concise discussion of 

 his recent theory of the mechanism by which the direc- 

 tion of incident light is perceived by plants. He 

 believes that the epidermic cells are, so to speak the 

 eyes of the plant. Thus, according to his view, when 

 light strikes a leaf at right angles to the surface it 

 results, from the plano-convex form of the epidermic 

 cells, that the inner wall of each cell is illuminated 



