xlvi REPORT OF THE STATE GEOLOGIST. 



FERTILIZERS. 



Under this heading might well be included everything that can be 

 applied to a soil for its amelioration or the increase of its fertility. 

 This would therefore, in its widest application, embrace even the addi- 

 tion of sands to clay soils of such sticky character as our famous black 

 waxy. The deposits, however, which will be mentioned here are Apa- 

 tite, Bat Guano, Gypsum, Glauconite (or Greensand Marl), Chalk Marl, 

 Limes, and Clays. 



APATITE. 



This mineral, which is a phosphate of lime, has as yet only been found 

 in very small quantities in Texas. Its value as a fertilizer is due to 

 its contents of phosphoric acid, and if it can be discovered in any quan- 

 tity will be of very considerable value in connection with the green- 

 sand and other marls in sandy lands low in that essential element. 

 Phosphate of lime is also the chief constituent of bone, and any depos- 

 its of this character will also prove of value. As yet known no de- 

 posits rich in phosphatic material have been found in Texas. 



BAT GUANO. 



As a fertilizer Bat Guano occupies a place second to nothing, except 

 it be the Peruvian guano. Its great value as a fertilizer is due to its 

 salts of ammonia, potash, and phosphorus. It is found in caves in 

 Williamson, Burnet, Lampasas, Llano, Gillespie, Blanco, Bexar, and 

 other counties of Texas in great quantities. It varies greatly in qual- 

 ity. Many of the caves are so situated that water has access to the 

 beds, and parts of the valuable salts of ammonia are dissolved and car- 

 ried off. In others, fires have by some means got started and immense 

 bodies of the guano burned. Many analyses have been made from 

 different caves, and large quantities of it have been shipped, but the 

 present lack of railroad facilities in the vicinity of the deposits has 

 prevented their successful working. 



Analyses of guano from Burnet and Gillespie counties gave a value 

 of over $50 per ton. 



GYPSUM. 



As a top dressing for many crops Gypsum is of great use, and when 

 ground for this purpose is known as land plaster. Ground Gypsum is 

 also an excellent deodorizer. 



