110 GLASS FOR OPTICAL PURPOSES 



There is an obvious remedy for the unremunerative rates for 

 optical glass, namely, that instrument makers should be prepared to 

 pay prices sufficient to make the industry financially sound. There 

 is also a means by which special glasses, required only in small 

 quantities, may be made without asking glass manufacturers to go 

 to unnecessary trouble and expense. It lies in the use of the joint 

 resources of the laboratories of the British Optical Instrument Manu- 

 facturers' Research Association, under Sir Herbert Jackson, and of 

 the Department of Glass Technology in the University of Sheffield. 



The last-named Institution has been equipped in such a manner 

 as to be admirably adapted for making special glasses in smaller 

 quantities than the manufacturer can consider worth while, and 

 meltings up to two cwt. in size can be undertaken. Where it is a 

 matter of importance that a special glass shall be worked out, I urge 

 most strongly that the joint resources of the two laboratories be 

 employed. 



In regard to crystals of calcium fluoride, I heartily concur with 

 Sir Robert Hadfield's views that it would be strange if the mineral 

 resources of the Empire could not furnish our requirements. Some 

 time ago I received from a merchant, Mr. B. Moss, 21, King Street, 

 Covent Garden, London, W.C., a beautiful specimen of crystalline 

 calcium fluoride from a mine in the neighbourhood of Johannesburg. 

 I am forwarding specimens of this to you. When I say that the 

 specimen was sent with the object of obtaining a market amongst 

 manufacturers of common glass articles only, it will be agreed that 

 the source may be worth further exploitation for optical specimens. 



The manufacture of optical glass in America, taken up only 

 during the war, is still a long way behind ours in output and variety. 

 Recently I was able to visit practically all of the war plants. The 

 number of types of glass made so far is limited, and in the last few 

 months all the plants except that of the Spencer Lens Co., at 

 Hamburg, New York, and the new experimental plant at the Bureau 

 of Standards, Washington, have closed down. For a long time, 

 therefore, there should be in America an important market for optical 

 glass made in this country. 



