NATURAL HISTORY OF THE DIATOMACEjE. 473 



This material is often almost white, but more commonly is tinted slightly 

 yellowish or salmon-colored. It makes up the most part of the material 

 of the coast range of mountains in California, and has also been found 

 in Peru, Japan, Algeria, Spain, and the West India islands. In Cali- 

 fornia, in the almost rainless districts, it is used for building, but gen- 

 erally is too friable for that purpose. The forms occurring in it are for 

 the most part discoid, with a few triangular ones, and, when prepared 

 and examined by means of the microscope, present one of the most 

 beautiful objects which can be so viewed. 



Something has been said with regard to the origin of the substance 

 known as guano, and which has been so extensively used as a fertilizer ; 

 but to the agricultural fraternity anything connected with this material 

 must prove of interest, so it is thought best to enter more fully into the 

 consideration of this subject on account of its important bearings, its 

 value to geologists, and its general attraction, evinced by the manner in 

 which the publications of the present writer thereon have been copied 

 and circulated by the periodical press. 



On May i, 1871, a discussion took place at the Lyceum of Natural 

 History, New York, on the subject of guano, when the Hon. E. G. 

 Squier exhibited a map of the Guanape islands of Peru, where guano 

 is found, drawings of a wooden idol and other objects discovered in the 

 guano, and photographs showing that that substance is distinctly strati- 

 fied, and not thrown down in the shape of a confused mass, as would be 

 the case if it were, as is usually supposed, merely the excrement of 

 birds and other animals deposited on rocky islands, in localities where 

 little or no rain falls to wash out its soluble and valuable constituents. 



Dr. A. Habel, who had visited the Chincha islands for the purpose 

 of studying the mode of occurrence of the guano (or, as he prefers to 

 write it, in consonance with the mode of its pronunciation, "whuano"), 

 made an extended communication showing that the outer and uppermost 

 portion of this substance does consist of the droppings of various spe- 

 cies of sea-birds and mammals, mixed with the feathers and eggs of birds, 

 and bones. This layer does not at all show signs of stratification, and is 

 of a reddish brown color. Below this is the guano proper, which is of a 

 different structure, and distinctly stratified. He says that "this stratifi- 

 cation is so marked that even a superficial examination must convince 

 VOL. i. 62 



