3o6 



NA TURE 



[January 14, 1909 



Bowling' and Low Moor iron. Copper is, of course, the 

 universal practice for stay bolts when a copper fire-box 

 is used. A copper stay bolt screwed into a copper plate 

 with its head carefully riveted over is more likely 

 to stand the wear and tear, since the coefficient of 

 expansion is the same. Leakage at the joints is re- 

 duced to a minimum ; the action of the fire on the 

 riveted head is far less severe, thus ensuring a far 

 longer life than if the stay was made of a bronze, 

 which naturally wastes with the fire action, the head 

 vanishing, and later on the shank of the stay bolt in 

 the copper plate for the same reason unless replaced 

 in time. Fig. 44 is a good illustration of this wear 

 and tear, although it is probably intended to illus- 

 trate a badly worn copper stay manv years old. 



Given a wider water space, and a pitch of stay 

 bolts less than the usual practice, then with the high 

 pressures now in use no trouble need be anticipated 

 from broken stays, and copper is evidently the proper 

 material to use, since it has to be fitted into a copper 

 plate and both exposed to intense heat. 



On the general design of boilers we find much 

 useful information, and reference is made to Mr. 

 Drummond's water-tube fire-box; surely the late Mr. 

 W. M. Smith, of the \orth-Eastern Railway, had a 

 good deal to do with the arrangement of the water 

 tube, it being originally fitted into the fire-box of North- 

 Eastern Railway engine No. i6ig in a somewhat 

 similar fashion. This engine is not mentioned, by 

 the way, in chapter xxxiii., dealing with compound 

 locomotives, although it is the progenitor of the Smith 

 type of three-cylinder compounds on the Midland and 

 Great Central Railways ; that is to say, the engine 

 is fitted with one high-pressure and two low-pressure 

 cylinders, the latter being used as high-pressure 

 cylinders and the former being in equilibrium when 

 starting a heavy train automatically. It is, of course, 

 well known that the three-cylinder Smith compounds 

 on the Midland have been fitted with a special regu- 

 lator valve, which does away with the Smith .-lulo- 

 matic valve. 



The question of compound working of iocomotivcs 

 has been a prominent one for a long time, and we 

 cannot congratulate the author on the way in which he 

 has dealt with it; surely four pages in a book of 300 

 pages is a ridiculous proportion to give us in a work 

 on the railway locomotive. All engineers are fully 

 aware that Mr. T. \V. W'orsdell was the inventor of 

 the two-cylinder compound locomotive ; why Mr. James 

 Worsdell should get the credit is a mystery. This is a 

 careless mistake for which there is no excuse. 



On the question of valve gear, expansion and link 

 motion, we find much information, but why " James 

 Stirling's " steam reversing gear is described as 

 " Wainwright's " might be explained; besides this, 

 the latest type of the Smith piston valve is not illus- 

 trated in Fig. 81. It is of the segmented type, and is 

 intended to free the cylinder of water when necessary, 

 being collapsible. The vacuum-destroying valve re- 

 ferred to has also been re-designed so far as to con- 

 stitute a lubricator as well, thus lubricating the 

 moving parts when running down hill with steam off, 

 a much desired improvement. 

 NO. 2046, vol.. 79] 



We have much pleasure in noticing these two 

 books; they have been written from such ditTerent 

 points of view that one forms the corollary of the 

 other. Locomotive engineers will do well to find a 

 place for both in their libraries. 



OUR BOOK SHELF. 

 Feste LosiDigen und Isomorphismiij. By Dr. 



Giuseppe Bruni. Pp. vi+130. (Leipzig: Aliadem- 



ische Verlagsgesellschaft, 1908.) Price 4 marks. 

 As an authority on the subject of solid solutions Dr. 

 Bruni has an international reputation, and it must 

 be considered a fortunate circumstance that the 

 Chemical Society of Breslau should have invited the 

 author to give a special lecture to its members, for 

 it is to that incident that the book before us owes 

 its origin. 



The theory of solid solutions put forward by van 't 

 Hoff in 1890 represents an extension of his well- 

 known theory of liquid solutions to the solid state of 

 aggregation. As a means of interpreting the vast 

 number of experimental observations which have been 

 accumulated since the date of its conception, van "t 

 Hoff's theory has been invaluable. The author is 

 one of its staunchest adherents, and has himself done 

 much to uphold the theorj' in the face of adverse 

 criticism. 



Dr. Bruni has retained the original form of the 

 address in tlie |)ublished text. The subject-matter of 

 the lecture, which occupies eighty pages, is divided 

 into two sections ; the first deals with the mode of 

 formation and the nature of solid solutions, the 

 second with the connection between the crystalline 

 form and the constitution of pairs of substances which 

 give rise to solid solutions. Explanatory notes, ex- 

 perimental data relating to the observations referred 

 to in the first part of the text, and references to 

 original papers which are in many cases accompanied 

 by critical abstracts, occupy the remaining fifty pages. 

 The arrangement is a most satisfactory one, and the 

 many references afford an excellent bibliography of 

 the subject. 



Not more than ten years ago a solid scilution was 

 regarded as somewhat in the nature of a rara avis. 

 The investigations of Roozeboom, Tammann, Kurna- 

 kow, Bruni, Carclli and others have, however, 

 necessitated a complete change in the attitude of the 

 chemist towards the conception. As showing the 

 general character of the phenomenon, the fact may be 

 cited that of one hundred and forty pairs of elements 

 examined by Tammann and his pupils, no less than 

 seventy-seven give rise to solid solutions, and in 

 twenty-three cases mixed crystals are formed whirii 

 contain the constituent elements in all possible pro- 

 portions. 



Most interesting is the author's account of the 

 application of the observed facts relating to the forma- 

 tion of solid solutions to the determination of the 

 configuration of organic compounds. That much 

 valuable information may be obtained from observa- 

 tions on syn-morphism (ability to form mixed crystals) 

 in connection with the solution of certain stereo- 

 chemical problems is clearly indicateil. It is, how- 

 ever, not only on account of its applications, but of 

 the intrinsic interest which attaches to the pheno- 

 menon that Prof. Bruni's lucid exposition of the sub- 

 ject of solid solutions and isomorphism may be 

 expected to meet with a favourable riception by a 

 wide circle of readers. Not merelv the chemist, but 

 the physicist, mineralogist, and geologist will find 

 much that bears on his particular subject in this little 

 volume. H. M. D. 



