deposits has been made in any one place. 1 There is especially a lack 
of information concerning the availability of the nitrogen and phos- 
phoric acid present in bat guanos and the availability of phosphoric 
acid in leached bird guanos. The solubility of the phosphoric acid in 
neutral ammonium citrate can not be considered a reliable measure 
of the availability until supported by vegetation tests, as this chemical 
method is largely empirical and not adapted to all classes of phosphatic 
fertilizers. 
In Porto Rico bat guanos have been used as fertilizers for many 
years to a limited extent, but without much idea of their real value. 
The contents of some caves have been examined at various times by 
different individuals, evidently with a view to exploiting them, but 
the small size of the deposits and the variation of the material prob- 
ably prevented this. 
For an intelligent utilization of these deposits it is obviously neces- 
sary to know the location and chemical analysis of the different kinds 
of material in each deposit and to have some general knowledge of the 
availability of the fertilizing constituents. In the following pages are 
given the locations of the different kinds of material in each cave, 
descriptions of the samples, chemical analyses, and the results of 
vegetation tests on the availability of the phosphoric acid and nitro- 
gen. On account of the great variation in the material, it was neces- 
sary to make a detailed survey in order to give the work local value. 
The availability tests have a certain value for bat guanos and leached 
bird guanos in general. 
DESCRIPTION OF GUANO DEPOSITS. 
EXTENT OF DEPOSITS 
The hundred or more deposits examined in Porto Rico were all 
found in limestone caves (see Appendix). The size of the indi- 
vidual deposits varied according to the number of bats, the size of 
the cave, and the protective conditions afforded. Most deposits 
were small, the largest being that of "El Oscuro" at Morovis, con- 
servatively estimated as consisting of about 3,000 tons. This agrees 
well with the reports of similar deposits in other countries, which 
apparently are very rarely of great size. The deposit near Cracow 
of 4,000 tons is spoken of as the largest European deposit. Ageton, 2 
however, estimates a deposit in Cuba as consisting of some 40,000 
tons of high-grade material. This is the largest deposit yet reported. 
i Analyses of one or more samples are given in the articles cited on page 3. R. F. Hare, in New Mexico Sta. 
Rpt., 1904, pp. 36-40, gives analyses of some 150 samples of bat guanos. Analyses of a few samples are 
to be found in Texas Sta. Buls. 35 (1895), 51 (1899), and 85 (1906), and in the fertilizer bulletins of some 
other State agricultural experiment stations. 
2 Ageton, C. N. Loc. cit. 
