GEOPHYSICAL LABORATORY. 137 



by 4. The correction of this Hmitation therefore also devolves upon 

 the pot industry rather than upon the glass-maker. 



Briefly, then, it has proved possible, in rather less than six months, 

 to produce optical glass from American materials in all the required 

 varieties and at a rate sufficient to meet current requirements. The 

 quality is also adequate for the present emergency. Of the limitations 

 which still confront us, none at the moment appears insurmountable, 

 though the production of melting-pots suitable for optical glass is a 

 serious problem which may require considerable time for its solution. 

 It is our present purpose, with the approval of the Trustees of the 

 Institution, to continue the investigation until the United States shall 

 be entirely independent of foreign sources of supply for optical glass. 



The remark has sometimes been made by casual observers that the 

 work of the Geophysical Laboratory, of all the departments of activity 

 of the Carnegie Institution of Washington, Ues farthest removed from 

 the practical needs of everyday life. So long as the earth remains 

 stable under our feet, it is sometimes deemed to be a work of superero- 

 gation to inquire closely into the details of its formation. In so far as 

 this view is real and not uncommonly met with, it will not be accounted 

 satire to call attention to the fact that the Geophysical Laboratory 

 was the first of the departments of the Institution to be called to meet 

 a practical emergency precipitated by war. Perhaps it is even a 

 matter of pardonable pride to all the members of the laboratory staff 

 that thi'ough the experience gained in their regular activities, and in 

 these alone, they have been enabled, in cooperation with wilUng manu- 

 facturers, to reach an extraordinarily rapid and successful solution 

 of so difficult a problem as the production of optical glass and to develop 

 processes, hitherto secret, to the point of successful, large-scale manu- 

 facture, within the short period of a few months. 



REPORT ON VOLCANO STUDIES AT NAPLES. (By Frank A. Perret.) 



A brief account of the volcanic research work accomplished during 

 the year must again be preceded, in simple justice, by a reference to 

 the difficulties incident to the still continuing state of war — difficulties 

 which tend to increase rather than diminish, and which must be imag- 

 ined rather than described. It is no exaggeration to say, however, that, 

 in spite of all, much has been done, and that along lines which, if not 

 those most spectacular and showing immediate fruit, are by far the 

 most important in the long run. 



Field research. — This branch of the work is that which is hardest 

 hit by existing conditions, which render traveling with instruments 

 almost impossible and justified only by events of the greatest impor- 

 tance. From this point of view, it is perhaps fortunate that the Italian 

 volcanoes have not led the volcanologist into temptation. With the 

 exception of an explosive phase at the new northeast crater of Etna, 



