NA TURE 



567 



THURSDAY, OCTOBER S, 190S. 



SUPERHEATERS. 

 Si(pcrhcat, Superheating, and their Control. By 

 William H. Booth. Pp. xv+155. (London: A. 

 Constable and Co., Ltd., 1907.) Price 6s. net. 



THE constant reiteration of one maker's name in the 

 book before us is wearisome, and we are agreed 

 that " Connected as the author is with the only type of 

 superheater using- water-control in inner tubes he is 

 not unnaturally apt to favour that system somewhat " 

 (p. 1^1,]. He does this to the extent of twenty-two full 

 pages of illustrations, &c., out of the 155 composing 

 the boo^, besides further references on nine more ! 



The author thinks regulation of the temperature of 

 the steam most important, and mentions seven ways 

 of accomplishihg this end. Prof. Unwin, however, 

 has expressed scepticism as to this necessity " pro- 

 vided onlv the superheaters is.'erc properly placed " ; an 

 opinion in which he was supported by the late Mr. 

 Bryan Donkin.' 



The author considers Lancashire and similar boilers 

 suitable for combining with superheaters, but for 

 " average water-tube boilers," whatever this may 

 mean, and marine boilers he recommends separately 

 tired superheaters. 



The inventor of one of the most widely used super- 

 heaters, especiallv for locomotive work, is referred to 

 as "one Schmidt," and two locomotives are stated 

 to have been fitted with his system with good results ! 

 While crediting another system with having been fitted 

 or ordered for 372 locomotives, he gives no descrip- 

 tion. Describing another in some detail, he says 

 nothing of its performance, or, indeed, whether it is 

 in use. Only two other superheaters are illustrated. 

 Particulars of two tests only are given, made with 

 " Cruse " and " Foster " superheaters respectively. 



.Although he works out the area of a " theoretical 

 diagram " to one ten-thousandth of a square inch ( !) 

 the author is less particular about other matters. For 

 instance, the specific heats of several of the substances 

 in a table on p. 8 do not agree with those on p. 148. 

 In a curious calculation on p. 16 he concludes that a 

 pound of steam at 361° F. will raise 60 pounds of 

 cast iron from 62° to 361°. Taking the value of the 

 specific heat of cast iron =o'ii, as given on this page 

 (two other values are given elsewhere), 1973 B.Th.U.^ 

 are required to effect this. As each pound of steam can 

 only supply 1192 B.Th.U., even if cooled to 32°, the 

 author expects to get more heat out of the steam than it 

 contains. 



In attacking what he calls " The Leakage School "' 

 he is apparently unaware that serious leakage is 

 usually only attributed to engines with flat slide 

 valves; and not, therefore, to those designed for use 

 with superheated steam. Captain Sankey has de- 

 monstrated in a masterly manner that properly de- 

 signed piston valves are practically steam-tight. 



On p. 29 the well-known expression PV''°'^ is 

 printed PS''""^' ; an unfortunate departure, as " S " has 



1 Proc. Inst. Mech. Engineers. 1896. 

 - (o'35i°-62')xo*iix6o=i973. 



NO. 2032, VOL. 78] 



another meaning on p. 33. .\nother loose expression 

 is the use of the term " thermometric " heat for a 

 quantit}- measured in B.Th.Li. 



On p. 34, the first equation is hopelessly wrong. A 

 formula at the bottom of the same page, for convert- 

 ing the actual evaporation of a boiler to its equivalent 

 weight of water " from and at 212," is only correct if 

 the steam is saturated and dry ; yet we read on p. 46 

 " No boiler delivers dry steam." 



Notwithstanding the author's statement that he 

 " prefers not to write a book of the catalogue-compil- 

 ation type," he has, in our opinion, failed to give any 

 information which would be useful to a designer, or, 

 indeed, to anyone but a prospective customer. 



The publishers have produced the book in their usual 

 excellent style, but there are one or two instances of 

 American spelling which have apparently escaped the 

 reader's notice. 



.4 BAV.i^RIAN TEXT-BOOK OF BOTANY. 

 Lehrhuch der Botanik jiir Oherrealschulen tind Real- 

 schulen. By Dr. Th. Bokorny. I. Teil. Pp. vi4-366. 

 Price 4 marks. H. Teil. Pp. 223. Price 3 marks. 

 (Leipzig : W. Engelmann, 1908.) 



A REDEEMING feature of the large number of 

 botanical text-books published during the last 

 few years has been the freshness, in some cases the 

 originality, of treatment which has from time to time 

 characterised them. The volumes now under notice 

 constitute a case in point. The reorganisation and ex- 

 tension of botanical teaching in the Realschulen and 

 Oherrealschulen of Bavaria has rendered the existing 

 text-books unsuited to the changed ideas, and in the 

 present volumes Prof. Bokorny has produced a text- 

 book which aims at directing, upon right lines, the 

 efforts of those entrusted with the new teaching. 



The author's treatment of his subject is of some in- 

 terest to teaching botanists. The first section of part 

 i., occupying nearly one-half of the volume, is con- 

 cerned with a description, in almost non-technical but 

 very direct language, of representative plant species 

 from the phanerogams downwards, the flowering 

 plants receiving by far the greatest attention. .\t con- 

 venient intervals in these descriptions the author deals 

 with a topic of special interest — not necessarily bear- 

 ing upon the preceding subject-matter— particular ex- 

 amples being the influence of soil conditions upon plant 

 life, the relationships between plants and insects in the 

 pollination processes, distribution of fruits and seeds, 

 and the influence of light upon plant growth. An almost 

 inevitable accompaniment of this system is a certain 

 discontinuity of text which is occasionally striking, but 

 there can be little doubt that the method should quickly 

 arouse the interest of the student, and found it, from 

 the beginning, upon an extended basis. The plants 

 chosen for description are invariably such as should 

 be familiar to students who are no longer beginners, 

 and a welcome departure from established custom is 

 the inclusion of plants of economic importance. The 

 descriptions are largely concerned with floral char- 

 acters, and are brief and well-written. 



The first section of the book, together with an out- 



A A 



