March 27, 1919] 



NATURE 



country, however, was felt at once on the outbreak 

 of war, when Messrs. Chance Brothers were able 

 to extend their resources, and, without outside 

 -assistance of any kind, to develop the manufacture 

 of all the types of glass required by opticians, 

 including some of the most extreme of the Jena 

 varieties, which became necessary owing to an 

 ■extended programme of work undertaken in con- 

 nection with photographic lenses for aircraft. 



In 1916 it was thought desirable (partly as a 

 precaution against the results of possible aerial 

 attack) that, for the manufacture of this important 

 material, the nation should not be dependent on 

 a single source of supply, and the Derby Crown 

 Glass Works, Ltd., were encouraged to commence 

 its manufacture, and they have already been suc- 

 cessful in producing a number of types of optical 

 glass of good quality. Still more recently the 

 United States, though, to a large extent, 

 <iependent on English and French resources for 

 -optical glass for war purposes, have commenced 

 its manufacture on their own account, and have 

 already achieved some success in this direction. 



Such are the demands of war on the optical 

 industry that towards the end of hostilities one 

 British firm was producing twice as much optical 

 glass as the world's total output previous to the 

 war. In considering, further, the position of the 

 industry after the war, it is therefore obvious that 

 there are resources in this country for the manu- 

 facture of all the optical glass which will be re- 

 quired by our opticians. Nor need there be any 

 apprehension regarding the ranges of glass which 

 will be available for the use of the lens designer. 

 Without any notable exception, Messrs. Chance 

 Brothers have been able, by their previous experi- 

 ence and by the work of their research laboratory, 

 established during the war, to produce glasses 

 which, in their optical constants, cover the full 

 range of glasses mentioned in the Jena list for 

 1913. 



The further development of the optical glass 

 industry would appear to be well provided for in 

 view of the practical research work carried out by 

 the manufacturer and of the more general work 

 conducted by the British Scientific Instrument Re- 

 search Association, recently formed under the 

 direction of the British Optical Instrument Manu- 

 facturers' Association. To maintain the supremacy 

 of the nation in regard to this manufacture, how- 

 ever, it is not only necessary to be able to produce 

 the material of good quality, but it is further 

 essential that it should be produced at prices which 

 will compete with those of foreign firms. With the 

 greater time which manufacturers will be able to 

 devote to the subject with this end in view, there 

 should be no difficulty in arriving at a satisfactory 

 solution of this point. 



However large the possible output and however 

 perfect the quality of British optical glass, the 

 future of the industry can be assured only if British 

 opticians are able to achieve and maintain 

 supremacy in home and foreign markets by excel- 

 lence in the design and workmanship of their 

 instruments of precision and by cheapness of 

 NO. 2578, VOL. 103] 



manufacture of the more common optical products. 

 Fortunately, there has been full appreciation of 

 this aspect of the situation, and in the Imperial 

 College of Science and Technology there is now 

 a Technical Optics Department, under the direc- 

 tion of Prof. F. J. Cheshire, and with the courses 

 of lectures given there, including those by so able 

 a computer as Prof. A. E. Conrady, the depart- 

 ment should greatly assist in ensuring that this 

 country is well supplied with expert designers of 

 optical systems. The wide increase in member- 

 ship of the Optical Society and the valuable papers 

 contributed thereto by workers in the National 

 Physical Laboratory and in the research depart- 

 ments of academic institutions and firms are also 

 of happy augury for the future. 



Before the war, computers designed lenses to 

 utilise existing Jena glasses of definite optical con- 

 stants. It would be undesirable and unfair to 

 British manufacturers to reverse this process com- 

 pletely. Computers should be prepared to do a 

 certain amount of recalculation, and so avoid im- 

 posing on the manufacturers the wasteful task of 

 producing a glass to imitate exactly the hazard 

 constants obtained in the particular foreign melt- 

 ing used previous to the war. 



SULPHURIC ACID AFTER THE WAR, 



THE Departmental Committee on the Post-war 

 Position of the Sulphuric Acid and Fer- 

 tiliser Trades, which presented a report, with 

 certain omissions and modifications deemed neces- 

 sary in the national interest, in February of last 

 year (Cd. 8994), has now issued an amended and 

 complete edition (Cmd. 23) in substitution for that 

 paper. 



The changes are not numerous, although im- 

 portant for the consideration of the matters with 

 which the Committee was concerned. They relate 

 principally to the pre-war production of sulphuric 

 acid; to an enumeration of the principal con- 

 suming trades and their estimated annual con- 

 ;Sumption prior to 1914; to the sulphuric acid 

 trade during the war, showing its enormous ex- 

 pansion; to certain statistical facts connected 

 with the development of the zinc industry during 

 the war, and its influence on the acid situation ; 

 to the probable post-war consumption of sulphuric 

 acid; and, lastly, to a list of acid factories owned 

 or leased by the Government, with their situation 

 and output. 



Although certain of the matters now dealt with 

 were probably known more or less accurately to 

 German manufacturers who had pre-war business 

 relations with this country, or kept them- 

 selves informed of its trade developments, it was 

 obviously undesirable that many of the facts 

 'brought to the knowledge of the Committee 

 should be published whilst we were actually at 

 war. Sulphuric acid is all-important as a prime 

 material in the manufacture of munitions, and it 

 need scarcely be said that the enemy would have 

 welcomed official information as to how far this 

 countrv was able to meet th$ sudden and unex- 



