ISO 



NATURE 



[December 19, 1901 



the book is higher than that at which they can be laid in 

 the neighbourhood of provincial towns. 



Nearly half the book is devoted to a description of the 

 materials used in the maintenance of roads and to their 

 petrology, a subject which should be carefully studied by 

 road surveyors. The authors very clearly show that it is 

 more economical to procure suitable material from a 

 distance than to employ local stones because the first 

 cost is less. There is a very considerable difference in 

 the wearing qualities of different kinds of stone, the 

 reasons for which are clearly shown in the book. 



The chapter on the construction of roads gives informa- 

 tion which is now little required in this country, but would 

 be of service to a surveyor in the colonies ; those on main- 

 tenance and cost contain a great many useful and 

 practical hints. The observations under the last head 

 are well worth the consideration of all authorities having 

 charge of the roads of this country. The authors em- 

 phasise what has often been pointed out — that good roads 

 can only be obtained by their being placed under skilled 

 management and by maintaining a high standard of 

 efficiency ; that roads maintained in good condition cost 

 less to keep up than those which are allowed to be 

 rutty, uneven and covered with loose stones and mud ; 

 and that while unnecessary expenditure is to be avoided, 

 the community ought to understand that money well 

 spent in skilled labour and good material is often saved 

 over and over again in time and convenience. 



Morpholoi^y of Spermatophytes. By John M. Coulter, 



Ph.D.," and Charles J. Chamberlain, Ph.D. Pp. 



x-t-l88. (New York: D. Appleton and Co., 1901.) 



Price 175 dollars. 

 For a long time past a comprehensive account of the 

 gymnosperms has been greatly needed, for within recent 

 years many important memoirs have appeared which 

 have thrown much light on the structure and relation- 

 ships of this interesting family of plants. It is, then, 

 with an anticipatory feeling of pleasure that one opens 

 the first instalment of Messrs. Coulter and Chanjberlain's 

 book on the morphology of the spermatophytes, seeing 

 that it is entirely devoted to the gymnosperms. And it 

 may at once be said that the authors have done their 

 work well. The book is more than a critical exposition 

 of our present knowledge, for it embodies also the results 

 of a considerable amount of original research on the 

 plants in question. The illustrations are many and 

 good, and include a large proportion of new figures. 



The main groups into which the authors divide the 

 family are dealt with in separate chapters, and Ginhgo is 

 treated as the representative of a division coordinate 

 with that of the Cycadales or of the Coniferales. The 

 chief fossil types are also considered, and a somewhat 

 detailed and illustrated description is given, based on a 

 study of Dr. Wieland's preparations, of the structure of 

 the strobilus of Cycadoiiij:a. 



A due proportion is maintained between the space 

 allotted to the account of internal microscopic structure 

 and of general morphology respectively, although natur- 

 ally the former, which includes the cytological details, 

 comes in for the greater share. Nevertheless, by no 

 means the least interesting chapters in the book are those 

 dealing with the comparative morphology and phylogeny 

 of the gynmosperms as a whole. The authors would 

 regard them as having a monophylctic origin, traceable 

 to a Filicinean ancestry through the Cycadofilices. They 

 base their opinion mainly on the undoubted descent of 

 the cycads from these forms, and on the difticulty of dis- 

 sociating the other gymnosperms from the cycads. They 

 do not, however, regard the connection between the dif- 

 ferent groups as a very close one, and suggest that the 

 Bennettitean stock may have served as the starting-point 

 for the cycads, whilst they would refer Ginkgoalcs and 

 Coniferales to a Cordaitean ancestry. 



NO. 1677, VOL. 65] 



They judiciously refrain from dealing very specifically 

 with the Gnetales. The three constituent genera, Gnetum. 

 Tumboa (a name which one regrets to see displacing 

 Welwitschia) and Ephedra differ so widely, both from 

 each other as well as from the rest of the main groups, that 

 they can only be regarded as isolated remnants of some 

 ancient line, the affinities ot which it is as yet impossible 

 to do more than guess at. 



A short sketch of the geographical distribution of the 

 gymnosperms brings the volume to a close. The authors 

 are to be congratulated on the ability they have dis- 

 played in producing a work which is valuable, not only 

 as a text-book, but as a real contribution to science. 



Guide Pratique pour les Calculs de Rhistance des chau- 

 dicres a vapeur ct F Essai des materiaux employes. 

 Par G. Huin et E. Maire, avec la collaboration de 

 H. VValther Meunier. "Actualities Scientifiques." Pp. 

 vi-F67. (Paris : Ciauthier-Villars, 1901.) Pricefr. 2.75. 



This book, consisting of a collection of data and tables 

 relating to boiler construction, is a translation of those 

 adopted by TUnion Internationale des Associations de 

 surveillance d'Appareils a Vapeur, which are in common 

 use in Germany. 



Part i. is devoted to formula?, supplemented by exten- 

 sive tables, for the determination of the dimensions of 

 the principal parts of boilers. 



Part ii. gives the rules relating to the selection of 

 the material and specifies the tests to be used in any 

 case. 



The whole book covers about the same ground as the 

 Board of Trade or Lloyd's rules for boilers, considered in 

 greater detail and the calculations assisted by tables. 

 The latter include, thickness of flue plates, for various 

 lengths, diameters and pressures, thickness of shell for 

 iron and steel, with various joints, dimensions and pres- 

 sures, and the thickness of fiat plates under various 

 systems of staying. 



The formuUc given are in nearly every case of the same 

 form as those used here, but generally speaking the con- 

 stants are such as to give slightly smaller dimensions. 



This is due to the use of an average factor of safety of 

 4'5 compared with 5 required by the Board of Trade. 



For the thickness of flue the formula given is Bach's 



(i+x/i4/Trf)+^-"' 



which should be applicable for a much wider range than 

 our simple 



V k • 



There is very little that is not to be found in an ordinary 

 engineer's pocket book. F. H. H. . 



Ein Wort iiber den Sits der vulkanischen Krdfte in der 

 Gegenwart. {Mitfhcilu/ie^aus dem Museum fiir Volkcr- 

 kttnde :u Leipzig.) \on Alphons Siiibel. Pp. 15 ; 

 9 figures in text, i coloured plate. (Leipzig: Max 

 Weg, 1 90 1.) 

 As such a difficult subject cannot be discussed in a short 

 notice, it must suffice to give the author's conclusions. 

 He regards the globe as originally a liquid mass, which 

 has become incrusted through loss of heat. This crust 

 at first would be thin and incapable of offering an effec- 

 tive resistance to the struggles of the liquid interior. 

 It would be ruptured at countless points, great floods of 

 lava would be outpoured, without, however, the building 

 up of important volcanic hills. At this epoch the earth 

 may have even been surrounded by a photosphere. In 

 the second stage the crust layer thickens to about lo 

 kilometres — the phenomena are similar in kind, but 

 correspondingly reduced in extent. In the third stage the 

 crust layer is about 25 kilometres, and the places of 



