476 



NA TURE 



[October 7, 1922 



function of statistics in the industry, are especially 

 good. 



In the space at our disposal, it is impossible to review 

 a work of this nature with justice, and likewise to in- 

 dulge in that amount of constructive criticism otherwise 

 desired ; we would suggest that, in view of its import- 

 ance as an ultimate source of fuel, considerably more 

 spare be devoted to the oil-shale question in future 

 edit Kins, while present refinery practice might with 

 advantage be much more severely criticised, both 

 with regard to technique and design. The author is 

 to be congratulated on the achievement of a remarkably 

 fine work, one that should be widely read by all serious 

 servants of a great industry. II. B. Milner. 



Our Bookshelf. 



Memoirs of the Geological Survey. Special Reports on 

 the Mineral Resources of Great Britain. Vol. 20 : 

 Lead and Zinc. The Mining District of North 

 Cardiganshire and West Montgomeryshire. By Dr. 

 O.T.Jones. Pp. vi + 207. (London: H.M. Station- 

 ery Office, 1922.) 7-?. net. 



Like the three previous volumes dealing with British 

 lead and zinc ores which have been issued by the Geo- 

 logical Survey, it must be admitted regretfully that 

 the present one has a scientific rather than an economic 

 interest. Some of the mines described in the present 

 volume, like Frongoch mine in Cardiganshire and the 

 Van mine in Montgomeryshire, have been extra- 

 ordinarily productive ; the former has been worked 

 for 59 years and the latter for 51 years, and from each 

 more than 100,000 tons of lead and zinc ores have been 

 produced in the course of its career, but in both cases 

 the really productive period was something like half 

 a century ago. The author suggests that it is just 

 possible that these mines might show an improvement 

 by sinking deeper and reaching harder rocks than the 

 soft shales in which they are now bottomed ; the 

 prospect, however, is not a very promising one, and 

 the present low price of lead affords no encouragement 

 to spend money on prospecting operations of a highly 

 speculative nature. 



The real value of the present work lies in the excellent 

 study of the formation of the faults and fissures and the 

 mode of their filling which Prof. Jones has supplied 

 in the introductory chapters. The first chapter on 

 the general structure of the area gives a very valuable 

 summary of its leading geological features, while the 

 next two chapters are devoted to a discussion of the 

 leading system of fissures to which the district owes 

 its mineral wealth. Finally, the last chapter deals 

 with a number of important points such as the probable 

 age and sources of origin of the ore filling, and the 

 influence upon it of the country rock traversed by the 

 fissures. These chapters form a most valuable con- 

 tribution to the study of mineral deposition, and from 

 this point of view, quite apart from any possible 

 remote economic possibilities, Prof. Jones's volume 

 deserves the careful attention of the student of mineral 

 deposits. II. L. 



Some Scottish Breeding Duck : Their Arrival and Dis- 

 persal. By Evelyn V. Baxter and Leonora J. 

 Rintoul. Pp. vii + 90. (Edinburgh: Oliver and 

 Boyd, 1922.) 55. net. 



The problems of the increase and extension of range of 

 ducks in Scotland, and in other countries, have long 

 exercised ornithologists throughout the British Isles. 

 As the authors of the volume under notice point out, 

 protection and a better feeling towards and a greater 

 interest in all wild birds are probably important factors 

 in the case but do not explain everything. Certain 

 species other than ducks are as steadily decreasing, 

 and the rise and fall of a species is a complicated 

 biological problem which may have but indirect 

 association with human interference, or may be due 

 entirely to other causes. The recent colonisation of 

 Scotland by other birds, such as the starling, turtle- 

 dove, and great-crested grebe, may be due to the 

 necessity for an over-abundant species to find new 

 areas and the possibilities of settling in an area where 

 raptorial birds and other enemies have been largely 

 destroyed by man's advance and action. 



One factor the authors have not stressed, the growing 

 habit of keeping pinioned ornamental fowl, though they 

 mention bird sanctuaries. Passing birds are often 

 " called down " by pinioned fowl, and some of them 

 may elect to mate and breed. That the direction of 

 spread differs in such ducks as the gadwall and wigeon 

 is no argument against this fact, for the source whence 

 come the visitors has no bearing on the influences 

 which cause them to remain. Many pairs of ducks 

 of various kinds have probably nested in out-of-the-way 

 places for years and been overlooked, for it is only 

 within the last thirty years or so that parts of Scotland 

 have been systematically explored from the ornitho- 

 logical point of view. Sportsmen and keepers are not 

 very particular about the species of the ducks which 

 fill their bags. 



We note that the authors use the correct spelling 

 of two much-discussed names, wigeon and shoveler. 



An Introduction to Engineering Drawing. Bv J. 

 Duncan. (Life and Work Series.) Pp. x+rs8. 

 (London : Macmillan and Co., Ltd., 1922.) 4s. 



The aim of Mr. Duncan's book is to enable young 

 students of engineering to produce intelligible work- 

 ing drawings of the details of engineering machines 

 and structures. The student is introduced to the 

 proper workmanlike methods of actual engineering 

 practice, and is not allowed the use of any special 

 hybrid methods which are supposed by many to be 

 sufficient for use in schools. 



The book commences with a description of drawing 

 instruments, their use and handling ; from this, the 

 student is led to the ordinary problems in plain 

 geometry with practical engineering examples such as 

 drawing cams, and plotting small surveys. After- 

 wards, a little solid geometry introduces the student 

 to oblique and isometric projection, and prepares him 

 for the drawing of engineering details. For this latter 

 portion of the training the author strongly recommends 

 the use of models. A commencement is made with 

 simple fastenings such as bolts and nuts, then the more 

 complicated connexions are dealt with, as exemplified 



NO. 2762, VOL. I io] 



