THE ORIGIN OF GUANO. 71 



micrometer as accurately as Is requisite in nearly all practical 

 applications. Subsequent trials have shown that the same 

 advanta<;es may be secured in a more satisfactory manner by 

 replacing the less dense flint glass prism by two, one of flint 

 and the other of crown, of such angles as give direct vision 

 for the whole combination of five. The dispersion is very 

 nearly the same as that of two prisms of ordinary flint glass 

 of 60'' angle." 



The Origin of Guano. — At ameetingof the Lyceum of Natural 

 History, of New York, Dr. Habel gave an account of observa- 

 tions made in the Chincha Islands, which lead to the conclu- 

 sion that guano is a stratified deposit. Professor Edwards 

 concurred in this view, which, indeed, he had previously 

 expressed in 1868. He writes : 



" When the portions of guano, which are insoluble in water 

 and acids, are examined by means of the microscope, it is 

 found to be made up of the skeletons of Diatomacai, Poly- 

 cystina, and Sponges, invariably of marine origin, and some- 

 times identical with those living in the adjoining ocean, and 

 fossilised in the adjacent Infusorial strata. Also we find that 

 some of these forms occur in patches exactly as they grow in 

 nature, and as they would present themselves if they were 

 deposited from water, and not as they would be if they had to 

 pass first through the alimentary canals of mollusca and 

 similar small animals, then through the same organs of fish 

 and birds, in turn, as they would have to do, to get into the 

 guano in the manner commonly supposed. 



" From all of these facts and others that I have collected of 

 no less importance, derived from chemical and microscopical 

 characters, I have come to the conclusion that guano is not 

 the excreta of birds deposited upon the islands and main land 

 after its upheaval, but that it is the result of the accumula- 

 tion of the bodies of animals and plants, for the most part 

 minute and belonging to the group which Haeckel has 

 included in a new kingdom, separate from the animal as well 

 as the vegetable under the name of Protista, and subsequently 

 upheaved from the bottom of the ocean. Subsequent chemical 

 changes have transformed it into guano, or heat and pressure 

 have so acted upon it that the organic matter has been 

 transformed into bitumen, while the mineral constituents are 

 preserved in the beautiful forms that make up the mass of 

 the extensive " Infusorial" strata, found in various parts of 

 the world." 



It is also stated that the anchors of ships moored in the 

 neighbourhood of the Chincha Islands constantly bring up 

 guano from the bottom of the ocean. 



