174 CARNEGIE INSTITUTION OF WASHINGTON. 



would certainly show marked explosion phenomena. Certainly the highly 

 oxidized condition of these gases, taken as they are from all sorts of promising 

 sources, argues strongly for some such hypothesis as that of Dr. Jaggar, of 

 combustion at or near the lava surface. 



(426) The manufacture of optical glass and of optical systems. A war-time problem. F. E. 



Wright, Lt. Col. Ord. R. C. Ordnance Department Document No. 2037, 

 pp. 309, 94 illustrations (1921). (Papers on Optical Glass, No. 40.) 



In this publication, prepared at the request of the War Department, a 

 general account is given of the processes of manufacture of optical glass which 

 were developed in this country during the war. The experience and knowl- 

 edge necessary to produce optical glass were gained at very considerable 

 expense and largely through the efforts of the Geophysical Laboratory in 

 cooperation with certain manufacturers. The purpose of this report is to 

 make available a small part of the information thus obtained. 



The book is divided into seven chapters. Chapter 1 outUnes the general 

 situation prior to the war, and includes a brief statement of the war-time pro- 

 duction of optical glass. In chapter 2 is given a detailed treatment of the 

 characteristics of optical glass. In chapter 3 the manufacturing processes 

 are considered in detail. Chapter 4 treats of the inspection of optical glass; 

 chapter 5, of the manufacture of lenses and prisms; chapter 6, of the inspection 

 of finished optical parts and of optical systems. Chapter 7 outUnes the optical 

 situation during the war; in it a summarized statement is made of the difficul- 

 ties encountered and of the measures taken to overcome those difficulties. 

 The several factors underlying the general problem of the production of optical 

 munitions during peace and war times are presented in detail, and inferences 

 are drawn regarding suitable methods for meeting the situation adequately. 



(427) The crystal structure of alabandite (MnS). Ralph W. G. Wyckoff. Am. J. Sci., 



2, 239-249 (1921). 



By a combination of a reflection spectrum from a known crystal face with a 

 powder reflection, and employing the general method based upon the theory 

 of space groups, it is shown that the arrangement of the atoms in alabandite 

 is either that of the "sodium-chloride grouping" or is a grouping approaching 

 very close to this arrangement. 



