802 



NATURE 



[August 26, 1920 



The matter sequence is curious. We start with 

 chain surveying and do not reach triangulation 

 until p. 377. Surveys for purely engineering ends 

 are often limited in extent, but none the less each 

 method has suffered from being considered on its 

 own merits and not as part of a whole. Geodesy 

 and topographical surveying are barely mentioned. 



We start with the field work, plotting, and area 

 computing of chain surveys. The subject is 

 clearly put,, and the investigations of errors and 

 of the accuracy of linear measurement are particu- 

 larly valuable. It is curious to find reference in 

 this chapter to British war maps, which owed 

 none of their characteristics to chaining. The 

 chapter on optics and on magnetism is welcome, 

 though it might with advantage have gone further. 

 After a description of instruments of minor im- 

 portance and of the vernier and micrometer micro- 

 scope, the author deals with theodolites, omitting 

 mention, unfortunately, of Messrs. Watts and 

 Co. 's latest patterns, which embody many im- 

 provements. Adjustments are fully described, and 

 are followed by a few pages on the accuracy of 

 angular measurements and on geodetic results. 



Having already dealt with linear measurement, 

 the author confines his description of traverses 

 mostly to angular measurement by compass, dial, 

 or theodolite. The investigation of errors of closure 

 is valuable and includes an interesting mathe- 

 matical analysis of Bowditch's rule. The surveyor 

 who traverses between stations of an existing tri- 

 angulation will find little help, however, for 

 the problems which then arise are prac- 

 tically ignored. Two consecutive chapters 

 deal with levels, levelling, contouring, trigono- 

 metrical levelling, and various relative and abso- 

 lute methods of determining altitude. Mention is 

 made of the Zeiss patterns of level in use on the 

 Ordnance Survey, but there is no mention of the 

 "water level " for contouring purposes. As usual, 

 the student will have no excuse for failing to 

 understand the relative values of different levelling 

 methods. There is a brief mention of precise 

 levelling generally, including a note on the new 

 geodetic levelling of Great Britain. Tacheometry 

 is thoroughly dealt with, the optics and attainable 

 results being lucidly described, and leads on to 

 range-finders, with special reference to the "Barr 

 and Stroud." The chapter on plane-tabling is not 

 so convincing as the rest, and is all too short. 

 The plane-table has been used with success in 

 climates as difficult as our own, and is an indis- 

 pensable method of survey. 



Chapters on curve ranging, earthwork calcula- 

 tions, and hydrographic surveying contain well- 

 arranged information rarely to be met with else- 

 where. It is under hydrographic surveying, 

 NO. 2652, VOL. 105] 



curiously enough, that one finds a description of \ 



instrumental resection. As a subject it deserves ! 



more attention than it gets, and should not be ' 



confined to a solution from three points. Tri- \ 



angulation and base measurement are well dealt : 



with and illustrated by historical references. The ' 



experienced surveyor will find little fresh informa- ] 



tion on astronomical surveying (except an inter- j 



esting note on Driencourt's prismatic astrolabe), ; 

 but will relish the simple and yet thorough way in 



which the theory is put. ; 



The concluding chapter, on photogrammetry, \ 



deals with the photo-theodolite and contains a brief ,; 



reference to stereophotogrammetry and to aero- ; 

 plane photography. The get-up, printing, and 



paper are a pleasure to see. All surveyors should i 



possess a copy of this book. j 



H. S. WiNTERBOTHAM. \ 



Australian Hardwoods. 



The Hardwoods of Australia and their Economics. 

 By Richard T. Baker. (Technological Museum, \ 

 New South Wales : Technical Education Series, j 

 No. 23.) Pp. xvi -1-522 + plates. (Sydney : The , 

 Technological Museum, 1919.) j 



THE author states in the preface to this work I 

 that his object is to make known to Austra- 1 

 Hans and the world generally the diversity of the \ 

 hardwoods with which Nature has endowed the 

 vast Australian continent. Such a book can 

 scarcely have been introduced at a more opportune \ 

 time, when the problem of how to provide sufficient i 

 timber for the world's growing needs has become ' 

 increasingly acute since the war. It is a remark- ■ 

 able fact that, while Australia has probably the 

 largest variety of hardwoods in the world, cover- 

 ing hundreds of thousands of square miles, the ■ 

 number of species they represent is comparatively 

 few^ — probably less than 500. Moreover, nearly { 

 half of these belong to the genus Eucalyptus, ■ 

 which covers at least two-thirds of the whole 

 surface, and supplies the bulk of hardwoods re- \ 

 quired for commercial purposes. 



The book is divided into three main sections. 

 Part i. deals with the physical properties of i 

 timber, colour, grain, taste, odour, structure, ;; 

 weight, durability, combustibility, and other ^ 

 features. The author emphasises the great aid '•■. 

 afforded by colour in the identification of Austra- 1 

 lian woods, and the fine series of chromatic plates ' 

 scattered through the volume, illustrating the 

 newly planed surface of all the important timbers, 

 shows in a very striking manner the great beauty \ 

 and variety of these woods. The writer of this 

 notice has had an opportunity of comparing ■ 

 a number of these plates with specimens in the j 



