December 15, 1910] 



NATURE 



199 



THE ORIGIN OF COAL. 

 Die Entstehung der Steinkohle tind der KaustobioUthe 

 uberhaiipt. By Prof. H. Potonie. Fiinfte Auflage. 

 Pp. xi + 225. (Berlin : Gebriider Borntraeger, 19 lo.) 

 Price 7.80 marks. 



THE study of the probable mode of formation of 

 coal and kindred substances has for many years 

 engaged the attention of Prof. Potonie, who, as 

 palaeobotanist in the University' of Berlin, and also as 

 a member of the Geological Surs'ey of Prussia, has 

 had exceptional opportunit}' for such study, both in 

 the cabinet and in the field. At the York meeting of 

 the British Association in 1906, he laid before the 

 Botanical Section his views on the origin of coal, 

 and the following year issued the fourth edition of 

 his little work, "Die Entstehung der Steinkohle, 

 u.s.w." — an octavo of only forty-seven pages, which 

 was briefly noticed in Nature (vol. Ixxviii., p. 86). 

 In the new edition, recently published, the work has 

 been considerably enlarged, and the title so modified 

 as to indicate that it deals with the origin of causto- 

 bioliths generally. 



Under this term caustobioliths are included all those 

 rocks or mineral substances which are, directly or 

 indirectly, of organic origin, and are combustible, 

 whilst such organic rocks as are incombustible, like 

 chalk, are distinguished as acaustobioliths. In order 

 to explain the origin of the fossil deposits, the author 

 has wisely given much attention to the corresponding 

 recent formations, or what may be reasonably re- 

 garded as such. Three great groups of caustobioliths 

 are recognised. In the first place, there are the rocks 

 called sapropelites, formed from organic slime, or 

 sapropel, resulting from the partial decay of aquatic 

 organisms and their products in stagnant water. 

 When the sapropel, in a sub-fossil state, becomes gela- 

 tinous, it is distinguished as saprocoll, whilst the 

 Tertiarj- forms are described as saprodil, and the 

 older varieties as sapanthracon. It is a disadvantage 

 that the work is rather heavih' weighted with an un- 

 familiar terminology, but it must be conceded that 

 most of the terms are expressive, and in many cases 

 undoubtedly convenient. 



Cannel coal, boghead mineral and many so-called 

 bituminous shales are regarded as sapropelites, whilst 

 petroleum is considered by Prof. Potonie to be a pro- 

 duct of the natural distillation of deep-seated sapropel 

 rocks, which have been exposed to heat and pressure 

 during processes of mountain-building. 



Another great group of caustobioliths is formed by 

 the humus rocks, which result from the accu- 

 mulation of the remains of land-plants and 

 bog-plants. This important class contains not only 

 many brown coals, but our ordinary- coals and anthra- 

 cites. Whilst sapropel rocks, generally present a dull 

 surface, or a silky lustre, and when heated yield much 

 gas, the humus rocks, or at any rate those of Palaeozoic 

 age, are usually lustrous and yield a smaller propor- 

 tion of gas. Coal which shows an alternation of 

 bright and dull layers is regarded as a mixed causto- 

 biolith, derived partly from humus, partly from 

 sapropel. 



NO. 2146, VOL. 85] 



To Prof. Potonie common coal is a rock which in 

 most cases has been formed where It is now found, 

 mainly by the fossilisation of deposits of peat, often 

 in far-stretching swamps. Considering the modern 

 tendency, especially in France, to regard most coal as 

 a substance of allochthonous formation, it is interest- 

 ing to find a distinguished specialist upholding the 

 view of " growth in place," which until recently has 

 been so much favoured in this country. 



Peaty deposits, though not formed of transported 

 material, may exhibit stratification, and humus 

 matter may be partially dissolved in water and pre- 

 j cipitated in layers. The coal-forming peat was prob- 

 j ably in a pulpy condition. In certain cases, the 

 , author suggests that the appearance of stratification is 

 ■ explicable as the result of pressure acting in a direc- 

 tion at right angles to that of the lamination. Prof. 

 Potonie holds that the flora of the coal measures 

 indicates a tropical climate, and cites instances of the 

 1 extensive growth of peat in tropical swamps, as in the 

 fens of Sumatra, described by Dr. S. H. Koorders. 

 Distinct from both the sapropelites and the humus 

 ' rocks is a small group of caustobioliths called lipto- 

 I bioUths, of which amber and pyropissite are examples. 

 \ The liptobioliths consist chiefly of resinous and waxy 

 1 substances, which by their resistance to decomposition 

 I are left after the decay of the other parts of the 

 I original organism. 



Throughout the work the author gives numerous 

 j references to original authorities, but unfortunately 

 i in most cases without sufficient detail, the reference 

 i being usually limited to the name of the author and 

 j date of pubHcation, such as "vergl. Uthemann, 1892." 

 The student seeking further information would be 

 i grateful for a little more definite guidance. 



F. W. R. 



THE VOICE AND SINGING. 



(i) The Brain and the Voice in Speech and Song. By 

 Prof. F. W. Mott, F.R.S. Pp. xi+112. (London 

 and New York : Harper and Brothers, 19 10.) Price 

 2s. 6d. net. 



(2) The Abuse of the Singing and Speaking Voice: 

 Causes, Effects, and Treatment. By Prof. E. J. 

 Moure and A. Bowyer, Fils. Translated by Mac- 

 leod Yearsley. Pp. xi+130. (London: Kegan 

 Paul, Trench, Triibner and Co., Ltd., 1910.) Price 

 2S. 6d. net. 



(3) The Voice. An Introduction to Practical Phono- 

 logy. By Dr. \V. A. .\ikin. Pp. ix+159. (Lon- 

 don : Longmans, Green and Co., 1910.) Price 

 75. 6d. net. 



THERE are now many manuals dealing with the 

 voice and with the management of the voice and 

 singing. These are unequal in value, more especially 

 as regards the description of the anatomy and 

 phvsiolog\- of the organs of voice and speech, and not 

 unfrequently the writer strongly advocates a view 

 peculiarly his own, and on which he founds his 

 method of training. It is therefore of importance to 

 have a description of the organs concerned in voice 



