NATURE 



[September 5, 1918 



things than they have ever done, but we think 

 thev will have to undergo a certain discipline of 

 conversion, and -forget a good deal of interior 

 competitive struggle, and of the outlook connoted 

 thereby, before they qualify for the premier posir 

 tion in the world's markets. 



THE CONSTITUTION OF COAL. 

 Monograph on the Constitution of Coal. By Dr. 

 M. C. Stopes and Dr. R. V. Wheeler. (Depart- 

 ment of Scientific and Industrial Research.) 

 Pp. 58 + plates iii. (London: H.M.S.O., 1918.) 

 Price 2S. net. 



IT is not too much to say that this monograph 

 forms the most important contribution 

 to our knowledge of what coal is, that has yet 

 appeared ; the problem has been tackled in the 

 right spirit and by workers with the right kind 

 of experience — namely, by a palaeobotanist and 

 a chemist working in conjunction. They them- 

 selves define the object of their research as an 

 attempt "to discover what the present actual 

 structure of a bituminous coal most usually is," 

 and they further define what they understand by 

 coal in the following words : " Ordinary coal is 

 a compact stratified mass of ' mummified ' plants 

 (which have in part suffered arrested decay to 

 varying degrees of completeness), free from all 

 save a very low percentage of other matter. ' ' 

 They themselves admit that this definition is not 

 satisfactory ; in particular it suffers from lack of 

 precision, as much depends upon the sense in 

 which the words "very low percentage" are 

 used ; it evidently includes lignite, which is per- 

 haps intentional, but it also must include peat, 

 which it was probably intended, to exclude. 



The monograph naturally falls into two main 

 parts, dealing respectively with the chemical and 

 the structural aspect of coal. The former dis- 

 cusses in much detail the composition of the vari- 

 ous component parts that have been more or less 

 completely identified, and relies mainly upon its 

 division into two distinct types of compounds, dis- 

 tinguished as the " cellulosic " and the "resinic, " 

 the distinction being based essentially upon the 

 solubility of the latter in pyridine, first discovered 

 by Bedson. 



In the latter portion much weight is given to 

 the work of Lomax, which showed that ordinary 

 bituminous coal is a humic accumulation in which, 

 not chiefly wood, but leaves, twigs, fructifications, 

 and other plant fragments preponderate, the term 

 " humic " being used to indicate that the accumula- 

 tion consisted of the largely undecayed mixed 

 organs of plants. The various distinguishable 

 plant remains are described and discussed, the 

 most important being the woody cells, bark, in- 

 cluding cork cells, cuticle, spore-coats and spores, 

 seeds, and soft-walled tissue ; it is shown that, 

 with the exception of resin, the cell contents of 

 the plants are but imperfectly preserved in coal. 



The authors summarise their researches by 

 stating their opinion that coal consists essentially 

 NO. 2549, VOL. IO2] 



of a conglomerate of morphologically organised 

 plant tissues, of plant substances devoid of mor- 

 phological organisation, of the comminuted degra- 

 dation products of both of these, and of "ulmins " 

 produced therefrom. But it may fairly be said 

 that the value of the work lies not only in the 

 results already attained, but also in the numerous 

 indications that it affords of the directions along 

 which future researches upon this highly complex 

 subject should be conducted. It is to be regretted 

 that the printing has been very badly done, and 

 that numerous clerical errors have been allowed 

 to escape the proof-readers. H. Louis. 



ANALYSIS AND GEOMETRY. 



(1) Elementary Mathematical Analysis. By Prof. 

 J. W. Young and F. M. Morgan. Pp. xii + 

 548. (New York: The Macmillan Co., 1917.) 

 Price 115. net. 



(2) A Course of Pure Geometry, containing a Com- 

 plete Geometrical Treatment of the Properties 

 of the Conic Sections. By the Rev. Dr. E. H. 

 Askwith. New edition. Pp. xi + 284. (Cam- 

 bridge: At the University Press, 1917.) Price 

 75. 6d. net. 



(1) ' I ''HE aim of Messrs. Young and Morgan is 

 -*- very clearly explained in their preface. 

 Their book is intended for first-year students in 

 universities and colleges, and, without in any way 

 neglecting practical methods and applications, they 

 have properly laid stress upon fundamental ideas 

 such as "function," "continuity," and so on. 

 Thus the student is prepared in due time for more 

 abstract and delicate theories, and preserved from 

 the risk of becoming a mere calculating-machine. 



The contents of the book are arranged in five 

 parts. The first is introductory ; it deals with 

 the idea of a function and its geometrical repre- 

 sentation, and gives a sketch of the theory of 

 rational operations in algebra. Part ii. considers 

 elementary functions, including the simply periodic 

 ones ; it also gives a chapter on computation, in 

 which there is an account of the slide rule, and 

 concludes with a chapter on implicit quadratic 

 functions. Part iii. contains the elements of ana- 

 lytical geometry as applied to the straight line, 

 circle, and conic sections. Part iv. comprises 

 chapters on algebraic manipulation, tactic, the bi- 

 nomial theorem, complex numbers, polynomials, 

 theory of equations, and determinants. Part v. 

 deals with functions of two variables, and gives 

 the elements of analytical solid geometry. Finally, 

 there are a set of useful tables, and a detachable 

 page from which a rudimentary slide rule can 

 be constructed. 



The present reviewer has lately been giving 

 lectures on similar, not to say identical, lines; the 

 agreement in aim, choice of topics, and extent of 

 treatment has been practically complete. It is 

 an encouragement to find one's ideas of a suitable 

 elementary college course so independently and 

 strikingly confirmed. We believe that treatises 

 of this kind will greatly help to establish a right 



