226 



NATURE 



[May 23, 1918 



with the machine upside down), it is still a matter 

 of contention as to the absolute degree of efficiency 

 which is required in regard to the labyrinthine 

 mechanism. 



On the other hand, in regard to the aural exam- 

 ination, it is beyond doubt that the candidate must 

 have good hearing, if only to detect the noise of 

 deifective working of his machine, and also 

 healthy tympanic membranes and uncongested 

 Eustachian tubes, so that he may readily adapt 

 himself to varying changes of pressure. 



Good muscular sense is of great importance in 

 a candidate, since there is reason to believe that 

 normally this plays intuitively a considerable part 

 in the accurate balance of a pilot and his machine. 

 Particular attention, therefore, is directed to this 

 point at the British Aviation Candidates' Board. 



In regard to reaction times these have been fully 

 investigated by the French authorities, but with 

 the present large demand for candidates for the 

 Air Force it is impossible and unnecessary to 

 carry out such tests in great detail, since during 

 his training this is done to a certain extent by his 

 instructor, and the candidate eventually allotted 

 to the type of machine for which, in this respect, 

 he is found most suitable. This, however, does 

 not mean that such tests should not be applied 

 in special cases. 



The flying temperament, it must be confessed, 

 rather baffles assessment, and at the present time 

 it is difficult to eliminate the candidate who may 

 develop an "anxiety neurosis," and therefore 

 later become unsuitable for flying. 



Valuable information is obtained from previous 

 medical history, and, to a certain extent, from 

 family history; it is deemed inadvisable, as a 

 general rule, to accept any candidate who has a 

 previous history of serious respiratory trouble or 

 nervous breakdown of any kind. In regard to a 

 history of concussion, however, it has been found 

 that 40 per cent, of successful pilots give a history 

 of concussion of varying duration. Therefore, if 

 at the time of examination there are no signs of 

 nervous instability, it shows that the candidate 

 has a nervous system which can recover well from 

 the effects of concussion. Also the history of the 

 accident leading to such concussion frequently re- 

 veals^ a degree of enthusiastic recklessness char- 

 acteristic of the "flying" temperament, and for 

 this reason the subject is likely to make a good 

 P'^°^- Martin Flack. 



THE ZINC ORE RESOURCES OF THE 

 EMPIRE. 

 nPHE Mineral Resources Committee of the Im- 

 J- perial Institute has arranged for the publica- 

 tion of a series of monographs on the mineral re- 

 sources of the Empire, of which the first, dealing 

 with zinc ores, is now issued. Copies of this 

 monograph are obtainable at 25. each, post free, 

 fiom the Imperial Institute. 



. Mr. S. J. Johnstone has been chieflv responsible 



for the work of compilation, and Mr 'T. Cook for 



that of general revision. They have been assisted 



by Mr. W. S. Robinson, vice-president of the Aus- 



NO. 2534, VOL. lOl] 



tralian Metal Exchange, and a member of the 

 Imperial Institute Committee for Australia. 



In issuing these monographs, the aim of the 

 committee is stated to be not so much to cater for 

 the specialist as to diffuse knowledge of the 

 Empire's mineral resources among those who con- 

 trol and sell them and those who use the products 

 to which they give rise, in the hope that the dis- 

 semination of such information will lead to a 

 greater utilisation of these resources within the 

 Empire itself than has been the case in the past. 



Although large quantities of zinc ore were 

 inined in the Empire before the war, nearly all the 

 product was exported to and smelted in Germany 

 and Belgium. Thus in 1913, although the Em- 

 pire produced 20 per cent, of the world's output 

 of zinc ores, its total production of the metal 

 (spelter) was only 6*4 per cent, of the world's out- 

 put, and not quite half of this was primary or 

 virgin spelter, the remainder being secondary (re- 

 melted) metal. Germany and Belgium, on the 

 other hand, produced about 48 per cent, of the 

 world's annual supply of spelter, although they 

 themselves contributed only 23 per cent, of th^ 

 world's output of zinc ore, the rest of their sup- 

 plies being obtained from the famous Broken Hill 

 concentrates shipped from Australia. 



In the last pre-war year Germany led the way 

 in ore-production, followed by New South Wales^ 

 the United States of America, Spain, and Italy, iri 

 order of magnitude. These are the principal ore-f 

 producing countries. 



The most important ore-minerals of zinc are the 

 sulphide, ZnS, known as zincblende and also as 

 sphalerite, and the carbonate, ZnCOg, known as 

 calamine and sometimes also as Smithsonite ; the 

 former is by far the more important source 

 of the metal. Special mention should also 

 be made of Franklinite, a mangano-ferrate of 

 iron, manganese, and zinc, found in large quan- 

 tities in New Jersey, U.S.A., which is a source 

 not only of zinc, but also of ferromanganese. The 

 silicate ore, hemimorphite, 3ZnOSi02+ HgO, also 

 serves as one of the minor sources of the metal. 



Zinc ores occur, and have been mined for some 

 time, in many parts of the United Kingdom; of 

 these a considerable proportion were exported 

 before the war to the Continent for smelting. On 

 the other hand, ores from foreign countries have, 

 at the same time, -been imported and smelted here, 

 a condition of things which would be incredible if 

 it were not true. 



The most considerable source of zinc ore in the 

 Empire is the deposit in the Broken Hill district. 

 New South Wales, which is situated at the 

 southern extremity of the Barrier range. The ex- 

 treme length of the ore-bearing ridge is about two 

 miles, and the report gives information as to 

 how the ore changes in passing, from the oxi- 

 dised outcrop to the unaltered sulphide minerals 

 below. 



Stated very briefly, this monograph gives, in 

 the first place, a short statistical account of the 

 world's production of zinc ores and zinc, and 

 describes the ore-minerals ; then follows a section 

 devoted to the principal ore-deposits of the Em- 



