Jan., 1916. Annual Report of the Director. 25 



as when all like material is together, yet the collections are consistently 

 available, until such time as they can be reassembled in the herbarium 

 hall of the new Museiun building. 



In the Department of Geology a complete readjustment of the cases 

 in Skiff Hall was made in order to give better lighting and group- 

 ing. Formerly the low cases had been arranged on one side of the 

 hall and the high cases on the other, but as the amount of light 

 obtained by this method of arrangement was insufficient, the cases 

 have now been arranged so as to form a series of alcoves with the 

 taller cases forming the sides of the alcoves and the lower ones oc- 

 cupying the center. The Hghting by this arrangement is much more 

 satisfactory. Six of these alcoves were placed on each side of the main 

 passageway through the hall, the forming of these alcoves having re- 

 quired the readjustment of 56 cases. From most of these cases it was 

 also necessary to entirely remove the specimens and reinstall them. In 

 this connection the opportunity was improved to perfect the order of the 

 specimens so as to bring related groups as close together as possible. The 

 exterior woodwork of the cases was also entirely refinished. Space was 

 fotmd in the cases for several new series, among them being a series of 

 bonanza silver ores from Mexico and a collection illustrating the natiu"e 

 and origin of certain "porphyry coppers." To the rare earths collec- 

 tion a radiograph was added made by exposing a lead object to the 

 emanations from camotite. This was installed with other radium 

 ores as a means of showing the best method of detecting such ores. 

 A portion of the collection of gold ores was removed to make room 

 for a model of a gold mine constructed by the Assistant Curator. This 

 model represents methods of working a small gold mine of meditmi rich- 

 ness in a vertical quartz vein six feet wide. The background and above- 

 ground scenery were prepared from studies of Arizona landscapes from 

 photographs made by the Curator. The model occupies a space of four 

 by three feet with a depth of about six inches. It illustrates a mine 

 worked by levels connected by a shaft. The ore is represented as a vein 

 of quartz containing minute particles of free gold. At one side the vein 

 is represented as intersected by another nmning from the front to the 

 back of the model. The ground about this vein is supposed to be looser 

 than at the side and a different method of timbering is illustrated. To 

 illustrate the methods of removing the ore several stopes are shown as 

 well as raises and winzes. Various features of mining eqtdpment are 

 also represented such as head frames, shaft house, tramways, ore cars, 

 ptmip, etc. The scale of the model is five feet to the inch, and pains 

 were taken to have it represent different features of a well managed 

 mine as far as possible. In all parts of the economic collections 



