H4 THE NEW WORLD OF SCIENCE 



of their influence upon light absorption, decolorizers may not 

 be used. Iron, copper, nickel, cobalt, chromic oxide, vanadium, 

 and manganese are to be avoided, both in the batch and in the 

 pot. Transparency is closely related to color in that the use of 

 decolorizers is prohibited, inasmuch as what they frequently do 

 is to form the color complementary to that of the glass, result- 

 ing in a gray which is very objectionable. Elements which 

 impart a high color must, of course, be avoided. 



Stability, hardness, and toughness are all properties which 

 may be largely controlled by the chemical composition of the 

 batch, the most desirable qualities being obtained in low alkali 

 glasses. 



It is apparent, therefore, that the production of good optical 

 glass falls into three or four principal problems, namely, raw 

 materials, good pots, special pots for special batches, tempera- 

 ture control, and glass stirring. From the nature of these 

 problems it is also clear that a good grounding in physics, 

 chemistry, and engineering is much more to be desired than 

 previous glass experience, the pre-war dogma of the Germans 

 to the contrary notwithstanding. 



The Pittsburgh laboratory of the Bureau of Standards con- 

 tinued its investigations and did what it could to place the infor- 

 mation gained at the disposal of the public. The glass manu- 

 facturers patriotically adhered to their determination to make 

 glass, but it was soon found that there were not enough trained 

 scientists actively engaged on the problem. It was late in 1916 

 that a new group began to become involved. Dr. F. E. Wright 

 was asked to give an opinion on the cause of milkiness and 

 clouds in certain glass, and while he professed no knowledge 

 at the time, he did endeavor to help. Later on the Council of 

 < National Defense became interested, principally through mem- 

 bers of the Naval Consulting Board, and Dr. Wright went to 

 Rochester to learn if cooperation would be welcome. In April, 

 1917, under the direction of Dr. A. L. Day, Director of the 

 Geophysical Laboratory of the Carnegie Institution of Wash- 

 ington, the first group from that laboratory went to the plant 



