602 SUMMARY OF CURRENT RESEARCHES RELATING TO 



chemical difficulties involved. Not the least of these is the selection 

 of materials for the manufacture of the melting-pots ; the preparatory 

 seasoning of the clay extends over months, or even years ; even when 

 at last moulded the pot requires a further seasoning of some six months. 

 The ingredients of the glass interact upon one another and also upon 

 the pot, which is liable to" be rapidly corroded away. The furnace gases 

 are extremely active and introduce many complications. The utmost 

 degree of purity is required in the constituents of the glass, A difficulty 

 from the British point of view is that no bed of sufficiently pure sand 

 exists in Great Britain ; but perhaps research might discover one some- 

 where in the British Empire. The sand required is, therefore, imported 

 into England from Fontainebleau, near Paris. Germany is fortunate in 

 possessing several good sources of pure sand, one of them having a 

 silica-content of 99'98p.c. 



In the third lecture the author discusses possible directions in which 

 the manufacture of British optical glass might be improved and de- 

 veloped so as to make this country independent of German compe- 

 tition. As many of the difficulties are connected with the chemical 

 action of the furnace gases acting on the contents of the pot, and, in 

 many cases, even through the pores of the pot-walls, the author discusses 

 the possible adaptation of a suitable form of electric furnace, in which 

 furnace gases would, of course, be totally absent. Then, if some 

 material could be found suitable for the pot itself which did not 

 chemically react upon the glass, an enormous piece of progress would 

 result. Then there is the question of whether glass is the only 

 crystalline substance suitable for lenses. The author thinks that in this 

 last direction modern research on the synthetic production of suitable 

 crystalline material may come to the rescue. At any rate, for an 

 investigator approaching this subject with adequate resources, a very 

 wide and promising field lies open. 



B. Technique.* 

 Zil) Collecting- Objects, including- Culture Processes. 



Automatic Delivery Apparatus for Fluid Media. f — S. W. Cole 

 says that during the course of bacteriological work undertaken for the 

 Medical Research Committee it was necessary to tube a given amount of 

 broth. For this purpose he devised a piece of apparatus. As will be 

 seen from the sketch (fig. 38), it consists of a stiff rubber ball (d) 

 attached by rubber tubing to a glass part, which contains two light 

 glass valves, accurately ground in. The fluid is placed in the beaker 

 and the rubber ball is squeezed by hand as much as possible. On 



* This subdivision contains (1) Collecting Objects, including Culture Pro- 

 cesses ; (2) Preparing Objects ; (3) Cutting, including Embedding and Llicrotomes ; 

 (4) Staining and Injecting ; (5) Mounting, including slides, preservative fluids, etc. ; 

 (6) Miscellaneous. 



t Lancet, Oct. 21, 1916, p. 716. 



