70 Report of the President 



MINERALS AND GEMS * 

 Herbert P. Whitlock, Curator 



To answer the question "What is a Mineral?" one side of a 

 large A-case in the Morgan Hall of Minerals has been utilized 

 for the display of a series of twelve group labels. 

 E P HT?t« Taken in order, these illustrate, by diagrams and 



annotated specimens, the extent of the portion of 

 the earth's crust from which we derive our knowledge of its 

 constituents; the proportion of the elements distributed 

 throughout this zone of rocks in the form of minerals; the 

 minerals exhibited in a piece of common granite; the elements 

 which combine to form these, and their relations as constitut- 

 ing mineral groups; how a mineral specimen differs from a 

 rock; what constitutes a mineral vein and how it is formed, 

 and what part water plays in the formation of minerals. 



A similar series, in course of preparation, has for its purpose 

 the demonstration of the grouping of particles of matter to 

 form crystals. Both of these exhibits are treated in a popular 

 way, calculated to appeal to the average visitor. 



During the year, the Department has contributed two illus- 

 trated lectures to the course prepared under the auspices of 

 the Yonkers Board of Education. These were 

 Extension delivered by the Curator, the subjects being "The 

 Water in the Atmosphere" and "Terrestrial 

 Water and Its Work in Forming and Transforming Earth 

 Matter." 



The Department has recently been able to add to its nega- 

 tives available for lantern slides a series showing the methods 

 of polishing diamonds. 



* Under the Department of Mineralogy (see also pages 212 to 214). 



