23 



lecture-rooms on heavily insulated wire with all possible precau- 

 tions. In the Petrographical Lecture Room this is utilized alter- 

 nately for illuminating the room by incandescent lights and by 

 means of a 2,500 c. p. arc lamp for microscopic projection or pho- 

 to-micrography with the large Zeiss apparatus placed there. In 

 this way brilliant projections of thin rock sections are shown to 

 the class in illustration of the lectures ; and for the ordinary screen 

 projection of photographs by lantern slides the same apparatus is 

 eminently satisfactory, especially since, owing to the great power 

 of the lamp, the projection can take place by daylight or by 

 partial darkening of the room. 



The instructor has continued during the year his work on the 

 Archaean of the New Jersey Highlands, and in the preparation of 

 a monograph on the Crazy Mountains of Montana. 



An exhibit in Petrography was prepared for the Chicago Expo- 

 sition as part of the contribution of the Department of Geology to 

 the general exhibit of Harvard University, comprising illustrations 

 of the methods of laboratory work and material for lecture illus- 

 tration, examples of the collections, etc. 



