392 Field Museum of Natural History — Reports, Vol. IV. 



specimens of gold in quartz and flake gold for comparative purposes and 

 selected specimens of fool's gold or pyrite, copper pyrite, native copper 

 in slate, and two specimens of mica, one of which is mixed with sand 

 and one is pure. To the collection of building stones exhibited, 27 cubes 

 and slabs have been added. A large specimen of fire clay from Missouri, 

 received in 191 2, has been installed in a case in this Hall, space being 

 obtained by moving some less important specimens. Some of the less 

 important pigments have been removed from their place of exhibit in 

 Hall 33 and in their place has been installed the collection of coal tar 

 products presented by the Barrett Manufacturing Company. The 

 production of dyes, etc., from these substances make them of especial 

 interest at the present time. Some additions have been made to the 

 coal mine model in order to make some of its features more readily 

 appreciable. Some of the underground portion has been cut away in 

 order to show the position of the ventilating shaft and its connection 

 with the hoisting shaft. This makes more evident the course of the 

 ventilating system. In order to make the exhibit of washed iron ores, 

 more instructive a small model of a log washer was constructed by the 

 Assistant Curator and installed in connection with that exhibit. The 

 model shows a trough containing a log bearing a series of fins arranged 

 in a screw-like manner; a hopper and track on which the unwashed 

 ores are brought to the washer; an engine house containing the en- 

 gine for providing power for operating the washer; and a car for remov- 

 ing the washed ore. A scale of one-third of an inch to the foot was 

 carefully adhered to in constructing the model, such a size having been 

 adopted in order that the model might not overbalance the collection. 

 The model is chiefly intended to assist the label in making the collection 

 more instructive. The usefulness of such models has been very favor- 

 ably commented on by visitors, on account of the ease with which the 

 details of the models can be studied as compared with the noise, confu- 

 sion, and complexity encountered in visits to large working plants. 

 Some improvements have been made in the installation of the collection 

 of petroleums shown in Alcove 107, chief among them being replacement 

 of the large two-gallon bottles of petroleum products by smaller bottles, 

 which are uniform in pattern with those in which the crude petroleums 

 are installed. The appearance of the collection has thus been much 

 improved. The installation of the other petroleum products has like- 

 wise been somewhat revised and improved. The series showing asphalts 

 and their uses received from the Barber Asphalt Company, with two 

 large photographs of Trinidad Lake, has been installed in Hall 35. 

 Several new specimens of graphite have also been added to the graphite 

 collection in this Hall. The specimens illustrating lithology and 



