244 



NATURE 



[November 28, 1918 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications.] 



Zeiss Abbe Refractometer, 



In reply to Mr. Simeon's communication published 

 in Naturi oi November 21, we would state that 

 oi the many different types oi Zeiss Abbe refracto- 

 meter, including a late pre-war instrument, thai have 

 passed through our hands for repair, all have been 

 fitted with an illuminating prism of low refractive 

 index glass (Nd about t-515). In every ease, by sub- 

 stituting an extra dense prism of suitable angle, we 

 have rendered the instrument serviceable for the 

 examination of liquids above 1-52. We discovered 

 this defect some time ago, and later directed the atten- 

 tion of Prof. Cheshire to it, communicating it to 

 Nature of June 21, nji; (vol. xcix., p. 331). We have 

 a number of these low-refractive index prisms which 

 have been removed from Zeiss refractometers, and 

 also a complete Zeiss instrument showing the defect 

 mentioned. It would, perhaps, be possible to arrange 

 to bring this instrument and the prisms to the next 

 meeting of the Optical Society, and if Mr. Simeon 

 would bring a Zeiss instrument having a pair of 

 extra dense prisms, a comparison would be interesting. 

 It is just possible that the Zeiss instrument to which 

 Mr. Simeon refers is one in which a dense lower 

 prism has been substituted. 



As we have already pointed out, in theory any glass 

 would make a suitable illuminating prism so long as 

 the roughened surface remains unimpaired, but in 

 practice the cleaning of the prism surface tends to 

 polish it, and as a result the illumination quicklv falls 

 almost to vanishing-point. L. BELLINGHAM. 



Bellingham and Stanley, Ltd., 



71 Hornsey Rise, N.19, November 22. 



BRITISH IRON-ORE RESOURCES. 

 /"\NE of the most marked effects of the war 

 ^-^ has been the stimulus that it has given to 

 the development of the mineral resources of the 

 British Empire, and particularly of those of 

 Great Britain. For many reasons the more active 

 exploitation of our home iron ores has been one 

 of the most prominent features of this movement. 

 Up to the invention of the Bessemer process the 

 iron industry of this country depended practically 

 exclusively upon domestic ores, the bulk of the 

 ores smelted being the claybands and blackbands 

 of the Coal Measures; in addition to these the red 

 haematites of the Mountain Limestone of the West 

 Coasl d ome of the Jurassic ironstones were 

 also worked, bu; up to about 1S70 the iron-ore 

 deposits of the Palaeozoic rocks formed the main- 

 stay of our British iron industry. When the 

 Bessemer proci introduced mild stee! as an 

 important factor in the industry, the relatively 

 small production of West Coast haematite no 

 longer sufficed lor our needs, and as mam of our 

 centres of iron-smelting are situated within easy 

 access of the coast, Bessemer ores were natu- 

 rally looked for abroad, and an energetic importa- 

 tion of foreign ores ensued. Bilbao ore was first 

 NO. 2561, VOL. I02] 



imported about 1870, and by 1878, after thi 

 Carlisi War, this importation had reached 

 850,000 tons; in 1913 the importation from Spain, 

 to which Almeria and other parts of Spain con- 

 tributed as well as Bilbao, was \\ million tons, 

 whilst our total imports from abroad, by far the 

 greater part of which was Bessemer ore, 

 amounted to about 7 A million tons. The domestic 

 Ore production was 16 million tons, of which 

 about 12 million tons came from the Jurassic 

 ironstones. The growth in the output of these 

 last-named ores was due in large measure to the 

 increasing adoption of the basic process of steel- 

 making. When the war rendered the importa- 

 tion of foreign ores difficult and expensive, out 

 iron and steel industry had to rely more and more 

 upon basic steel produced from the latter class of 

 ore. This development has been favoured by t be- 

 grudging recognition that for most purposes basic 

 steel properly made is as good as acid, and 

 furthermore by the abandonment by the Board of 

 Agriculture of the so-called citric acid test for 

 basic slag in favour of its valuation by the total 

 phosphoric acid present ; this means that whereas 

 under the former "made in Germany" test thou- 

 sands of tons of British basic slag had to be 

 dumped out at sea as unsaleable, such slag can 

 now be utilised and its phosphoric acid contents 

 rendered available for the British agriculturist. 

 At the same time, the British steel trade now has 

 a market opened up for what was before a waste 

 product. 



One of the signs of the increasing interest taken 

 in domestic ores is the attention that is being 

 devoted to the study of our iron-ore resources. 

 Apart from some earlier descriptions of British 

 iron ores, which have to-day at most only 

 an historical interest, the first attempt at a 

 real estimate of our iron-ore resources was 

 that published by the present writer in the 

 important treatise issued by the Eleventh 

 International Geological Congress at Stock- 

 holm in 1910. This showed for the first time 

 the magnitude of Britain's iron-ore reserves, and 

 attracted much attention on the Continent ; it 

 would be interesting to speculate how far it may 

 have contributed towards Germany's intention to 

 bring about the war, one of the main motives of 

 which was Germany's desire to obtain possession 

 of the French iron-ore fields and thus to outstrip 

 all competition by commanding f.ar the largest 

 iron-ore supplies of Europe. The principal 

 value of the above-named estimate to-day lies in 

 tile fact that it has formed the basis of newer and 

 more accurate estimates. Since the beginning of 

 the war three important contributions to our know- 

 ledge of our own iron-ore resources have appeared, 

 each under the auspices of a Government 

 department it need scarcer) be added, having 

 regard to our characteristic British methods, a 

 different department in each case, working inde- 

 pendently of the others. Nothing could In- moo 

 eloquent of the need for a central administration, 

 co-ordinating such efforts and avoiding useless 

 duplication of work. The first was the now well- 



