378 



BEPOET OF NATIONAL MUSEUM, 



The Pedro Keys, Redonda, Alta Vela, and some others differ in car- 

 rying larger percentages of alumina and iron oxides, necessitating 

 special methods of preparation. 



Deposits of leached guano of considerable extent have existed on 

 several islands of the Polynesian Archipelago, in the Pacific Ocean, the 

 better known being those of Bakers, Rowland, Jarvis, Malders, 

 Birmie, Phoenix, and Enderbury islands. The deposits are described l 

 as varying from 6 inches to several feet in thickness, of a whitish- 

 brown or red color, pulverulent when dry, sometimes in the form of 

 fine powder and again in coarse grains. Though closely compacted, 

 the material can as a rule be readily removed by pick and shovel. The 

 purest varieties are those lying on the unaltered coral limestones, of 

 which the islands are mainly composed. Those lying upon gypsum 

 have become contaminated with sulphate of lime. In places the 

 deposits are covered with a thin crust due to the action of atmospheric 

 agencies. On Jarvis Island a considerable share of the deposit is covered 

 by material of this crust-like character. Such on analysis are found to 

 contain less water and a corresponding higher percentage of lime and 

 phosphoric acid than the loosely compacted material, being indeed, as 

 shown by Mr. Hague, a nearly pure diphosphate of lime. The following 

 analyses show the general character of these guanos from Bakers Island, 

 No. I being freshly deposited and consisting of the dung of the frigate 

 bird (Pelicamts aquihis). No. II is a light-colored variety from a deep 

 part of the deposit, and No. Ill dark guano from a shallow part. 



Afialyses of guano. 



BAT GUANO. The dry atmosphere of caves preserves indefinitely the 

 fecal matter of bats and such other animals as may frequent them. 

 Such under favorable conditions may accumulate in sufficient quanti- 

 ties to become of economic importance, being gathered and used as a 

 fertilizer under the name of bat guano. The usual form of the 



1 J. D. Hague, American Journal of Science, XXXIV, 1862, p. 224. 



