THE NONMETALLIC MINERALS. 379 



entrances to caves is, however, such as to make the process of removal 

 tedious and expensive. 



Bat guano is, as a rule, darlc in color, of a glossy, almost nnicilagin- 

 ous appearance, and quite hard (Specimen No. 58358, U.S.N.M., from 

 Cioshen caves, Juab County, Utah). Its composition is shown in the 

 following analysis of a sample from the Wyandotte caves ' in southern 



Indiana : 



Loss at red heat 44. 1 



Organic matter 4. i)() 



Ammonia 4. 25 



Silica 6. 13 



Alumina 14. 30 



Ferric oxide 1-20 



Lime 7. 95 



Magnesia 1-11 



Sulphuric acid 5. 21 



Carbonic acid 3. 77 



Phosphoric acid 1 . 21 



Chloride of alkalies and loss 5. 82 



100. 00 



According to the reports of the State geologist, the caves in the Si- 

 lurian strata in Burnet County, Texas, are in many instances enor- 

 mously rich in bat guano. The following description of one of these 

 caves is taken from the report for 1889: 



The bat cave in the northwest corner of Burnet County is worked by a Georgia 

 company, and I learn from the men there that about 157 tons of the material had 

 been shipped up to December 20, 1889. The shipments are made by wagon to 

 Lampasas, Texas, and from there by rail to Georgia and other parts of the United 

 States. The cave is situated about 8 miles from Bluffton, going north up Beaver 

 Creek. Near Lacy Branch, a tributary of Beaver Creek, about 2 miles north of 

 Silver Mine Creek, there is a fault on the west side of Beaver Creek, in a branch 

 which is called "Bat Cave Hollow." Proceeding from this point in a northwest direc- 

 tion for about 2 miles we reach the bat cave, on top of a higher chert bed. The way 

 from Beaver Creek to the cave is constantly ascending, first over Silurian limestone 

 for about 1 mile, when the chert formation appears. On the top of a chert hill 

 there is an opening of about 10 feet in diameter, extending perpendicularly down- 

 ward for 30 feet, where, at the north side of this opening, there is an entrance to the 

 cave. The cave has not been measured, but I estimate its length from north to 

 south to be about 600 yards, with as much if not more space in the opposite direc- 

 tion. The top of the cave, as well as its sides, is solid chert, such as occurs in all the 

 chert beds in San Saba and all the neighboring counties. The guano bed in the heart 

 of the cave has been burned, leaving the ashes at places 26 feet deep, and not less 

 than 18 feet at others. The ash is not brought up, and the supply of guano is taken 

 from the surrounding portions and sides of the cave. As I understand, there are 

 some leaders to the cave that have not yet been explored, there being plenty of ma- 

 terial near the heart of the cave for all present requirements. Five men were em- 

 ployed in digging and bringing out the guano by means of a rail track to the surface, 

 where it is deposited upon a large platform erected for that purpose. 



1 Geology of Indiana, 1878, p. 163. 



