244 



NA TURE 



[Al'KIL 29, 1909 



their pasty stages. The hardness of allojs was found 

 to be due in many cases to the formation of inter- 

 metallic compounds, and straightway the conditions of 

 formation of numbers of these were investigated. The 

 toughness and ductility of alloj's were seen to be con- 

 nected with their structure, and the effects of anneal- 

 ing, quenching, and the like on the structure were 

 accordingly subjected to careful scrutiny. It is natural 

 for scientific observers to lose sight of the practical 

 bearing of their work, and to wander, in the author's 

 words, " in the intricacies of solid solutions, hyper- 

 eutectics, solidus curves and phases," whither the 

 manufacturer refuses to follow them. It has been 

 Mr. Law's business to show that there is another side 

 to research, and that something has been done besides 

 the manufacture of a set of new labels. 



On the whole the result of his labours is promising. 

 The book is written in an easy conversational manner, 

 which encourages the reader to continue seeing what 

 the author has to say. About 100 pages are devoted 

 to the general properties of alloys and the methods of 

 investigating them, and the remainder to special 

 descriptions of particular alloys. Only those employed 

 in the industries are dealt with, and though at first 

 sight this seems to leave many gaps, we are reconciled 

 to the method as we realise how much space is saved 

 for useful and practical remarks. 



Both sections have been carefully prepared, and 

 mistakes are far from numerous. Among those 

 noticed is the statement on p. 219, and again on p. 221, 

 that s per cent, of cadmium is added to standard silver 

 in America as a deoxidant. This should, of course, be 

 5 per 1000. Then the definition of " isomorphous " in 

 the glossary, " a term applied to crystals exhibiting 

 similarity in form," leaves much to be desired. The 

 " glossary of terms " generally is weak, alike in respect 

 of omissions and of inexactness. The author is 

 happier when dealing with photomicrography. Both 

 the colour photographs reproduced in the frontispiece 

 and the series of plates at the end of the book are 

 really handsome illustrations of the structure of metals, 

 and are far in advance of the smudgy photographs or 

 diagrammatic drawings usually associated with such 

 work. T. K. R. 



ASTRONOmCAL DETERMINATION OF 

 POSITION FROM BALLOON. 

 Astronomische Ortshestimmung Im Ballon. By Prof. 

 Adolf Marcuse. Pp. 67. (Berlin : Georg Reimer, 

 1909.) 



' I "HE great advances made in aerial transit, by 

 J- which long-distance voyages are rendered possible 

 by ordinary spherical balloons, while hundreds of 

 miles may be travelled by dirigibles, and the prospect of 

 long-distance voyages in the rapidly improving aero- 

 planes, suggest at once the important problem of the 

 determination of the astronomical position of these 

 craft at any moment. 



During the daytime, while the earth is in view and 

 not rendered invisible by cloud strata below, the experi- 

 enced aeronaut can easily locate his position by means 

 NO. 2061, VOL. 80] 



of the many excellent large-scale charts at his dis- 

 posal. On clear nights, by means of the light of the 

 moon, he is also able to follow his course, and, 

 failing the moon, he can pick up his whereabouts by 

 closely observing the lighted-up cities and towns as he 

 approaches them. 



With, however, no glimpse of the earth below him, 

 the only two facts which he has in his possession are 

 his height from the ground and the magnetic cardinal 

 points. 



In a spherical balloon this knowledge does not 

 inform him whether he is travelling in a northerly, 

 southerly, easterly, or westerly direction. In a dirig- 

 ible he may head his craft in the direction of any of 

 the points of the compass, but then his leeway will be 

 an unknown, probably a very considerable, quantity, 

 and he will soon find that his position in relation to 

 the earth's surface is unknown. 



For navigating purposes it is as important to know 

 exactly where one is when travelling in the air as it 

 is to a sailor when his ship is ploughing the ocean. 



The volume before us is therefore very welcome, for 

 Prof. Marcuse brings together, in a very concise and 

 simple manner, methods which can and have been 

 employed on actual voyages. It must be understood, 

 in the first instance, that very rigid determination of 

 position cannot at present be attempted. In the first 

 place, the basket of a balloon is seldom steady, and is 

 nearly always in a slow state of rotation. Again, the 

 envelope above the observer cuts off a considerable 

 portion of the sky that would be available under land 

 or sea conditions, but against this he is in an elevated 

 position and his horizon is clearer. Possibly better 

 observations can be made from the platforrris of 

 dirigibles than from the baskets of spherical balloons. 



The instruments necessary for the determination of 

 the latitude and longitude, to which reference is made 

 in this book, are the level-quadrant for the observation 

 of altitude, a chronometer for recording Greenwich 

 time, and a fluid compass with an alignment addition 

 for azimuth observations. The first portion of the book, 

 parts i. to iii., deals with the instruments, their use, 

 and the general nature of the problems to be solved. 

 Part iv. is devoted to the formulse, forms for working 

 them out quickly, and numerous worked-out 

 examples ; this portion is divided into two parts, 

 treating of day and night observations. In part v. 

 the use of the tables given at the end is explained in 

 detail, and a description is also given of the charts 

 which conclude the book. These maps include a 

 chart of the northern hemisphere, showing the 

 brighter stars which are best available for use, and 

 following this are two magnetic maps, showing by 

 isogonic lines the deviation of the compass from the 

 true meridians for the year 1909 for (a) the whole cf 

 Germany and (6) for Europe. 



This brief summary of the main features of this 

 book shows that it is well adapted for the purpose it 

 has in view. British aeronauts should therefore make 

 themselves acquainted with some of the methods here 

 expounded, for the subject will increase in importance 

 as years go by. 



W. J. S. LOCKYEK. 



