392 



NATURE 



[September 29, 1910 



of a special chapter on paljEobotany, a branch of study 

 conspicuously absent from Sachs' history, for before 

 i860 our knowledge of fossil plants, based mainly on 

 plant impressions, was too inexact and too uncertain 

 to be of much value in the discussion of the relation- 

 ship of plants. 



But with the publication of the classic memoirs of 

 Renault and of Williamson a precise knowledge of 

 the extinct vegetation of at least one geological period 

 led to striking- advances in our knowledge of the 

 extinct vascular cryptogams, and the discoverv, at 

 the beginning of the present ccnturv, of the seed- 

 bearing nature of many of the fern-lilve plants of 

 the Carboniferous period, led to a remarkable advance 

 in our conception of the course of evolution of plants 

 and an unexpectedly complete vindication of Hof- 

 meister's views. There is no more striking testimonv 

 of the stimulus given to the study of palaeobotany by 

 Renault and Williamson than the band of still active 

 workers in France and England, the work of which 

 is passed in review in chapter v. 



It is perhaps in consonance with the general trend 

 of advance in botanical science that physiology should 

 receive a fairlv lengthy treatment, but a perusal of 

 book iii. certainly gives the reader the impression that 

 the author has given a somewhat more detailed 

 account of the problems of this branch of botany, and 

 that subjects of equal importance connected with the 

 anatomy of plants have been less generouslv treated. 



One must take into consideration that none of the 

 chapters on phvsiologv deal with the physiology of 

 the reproductive processes. These are dealt with 

 partly in connection with the alternation of genera- 

 tions, and partly in connection with the morphology 

 of the flower. But the physiology of reproduction 

 really merits a chapter to itself, in which the modern 

 views of the nature of fertilisation might have been 

 more fully set forth, and the splendid work of Dar- 

 win and Muller on self- and cross-fertilisation might 

 then have received ampler treatment. 



Grateful as we feel to Dr. Green for the sum- 

 maries of work done in the various fields of botany, 

 and recognising fully their usefulness, we close the 

 book with a feeling that it lacks the breadth of treat- 

 ment and the perspective of Sachs' history. But in 

 making this somewhat invidious comparison, we do 

 not wish to detract from the careful and painstaking 

 work of the author, which is shown by the very large 

 number of books and papers which he passes under 

 review. His task has been doublv difficult, partly 

 owing to the fact that he has had to deal with 

 innumerable memoirs rather than with a smaller 

 number of great works, and partly owing to the fact 

 that he has been called upon to write the history of 

 a comparativelv short period of scientific advance, a 

 period, moreover, so recent as to make it difficult to 

 get a proper perspective. These difficulties might 

 have daunted the most courageous, and we feel duly 

 indebted to Dr. Green for undertaking the onerous 

 task and providing us with so useful a summary of 

 the work done during the latter half of the nineteenth 

 century in so many fields of botanical research. 

 NO. 2135, VOL. 84] 



FUELS AXD FURXACES. 

 Fuel and Refractory Materials. By Prof. .\. H. Sex- 

 ton. Second edition. Pp. x + 364. (London : 

 Blackie and Son, Ltd., 1909.) Price 55. net. 



THIS work deals generally with natural and pre- 

 pared fuels, with coal-washing, recovery of by- 

 products, the types of furnaces for metallurgical pur- 

 poses, with the working of these furnaces in regard 

 to the economical use of fuel, with the measurement 

 of the high temperatures produced, and the commer- 

 cial testing and calorimetry of fuels, as well as with 

 the natural refractory materials and the apparatus 

 made from these. 



The book is packed with information on this very 

 extensive subject, although it is a little loose in places, 

 sometimes in expression, at others with regard to 

 information given. 



On p. 39 calorific power is defined as the heat 

 evolved, which is ambiguous. On p. 59 coal is stated 

 to be the only important fuel except natural gas and 

 oil, but for much special Government work and for 

 the higher class .Shetfield steels, the irons made with 

 charcoal fuel in Sweden and elsewhere are of the 

 greatest importance ; also, later, it is stated that char- 

 coal has been used in blast-furnaces, whereas at least 

 quite recently there was charcoal pig-iron being made 

 in one blast-furnace in Cumberland, and it is also 

 e.xlensivelv made in such countries as Sweden. 



The time-honoured diagrams of charcoal burning in 

 piles remind one how they shocked the commercial 

 sensibilities of a former student, -who was also a 

 Swedish ironmaster, as all the beautifully arranged 

 trunks shown would, according to him, have been cut 

 up into planks for sale, and visits to several charcoal- 

 burning districts confirmed the statement. 



Coalite, the product of the coking of coal at a barely 

 visible red-heat, is just mentioned, and as this new de- 

 parture in coking is creating such an amount of 

 interest in the hope that it may help in the future to 

 reduce the smoke produced in those worst of offenders, 

 domestic fire-grates, one would have liked a little 

 more said about coalite. 



A good account is given of fuels generally, but the 

 cost of illuminating gas is stated as varying from 

 2s. 6d. to Ss. per 1000, whereas in Sheffield it varies 

 from li. 4^. to is. per 1000 cubic feet. 



The description of the use of steam in producers is 

 very well done, but the statement that no producer 

 is satisfactory that allows any sensible amount of 

 CO„ to pass into the gas is too severe, as in ordinary 

 works practice it is not feasible to reduce the CO, 

 below 4 to 6 per cent, by volume, and there is no 

 advice given on the important matter of the thickness 

 of the bed of fuel that should be kept for normal 

 working. 



Silicon, manganese, &c., important fuels in metal- 

 lurgical operations, are not mentioned. 



In dealing with standards of temperature it is not 

 clearly enough stated that the present accepted 

 standard is the gas thermometer, and in the descrip- 

 tion of the Wanner pyrometer, the statement that 



