474 PHYSICAL GEOGRAPHY. 



every unprejudiced person that it is the product of sedimentary for- 

 mation. It is made up of alternate white and yellow strata, varying 

 in shade and thickness. All of these strata exhibit distinctly their 

 inclination or dip, which varies not only on the separate islands, but in 

 different parts of the same island. On the middle island, for example, 

 the inclination or dip of the strata in one part of it does not amount to 

 more than five degrees, while in another part it is eight degrees, and in 

 a third, close to the first, fifteen degrees." In one place strata, running 

 south-west and north-east, and dipping twenty degrees, rested uncon- 

 formably on others running north and south, and dipping only four 

 degrees. In all of the strata are imbedded stones of various sizes and 

 weight up to fifteen pounds, as well as eggs and bones. Another proof 

 that the guano has been deposited beneath the ocean is seen in the 

 various strata of sea sand underlying it, and which are also stratified, and 

 dip in one direction or the other. 



The present writer said that he first made his hypothesis public, with 

 regard to guano having been deposited beneath the water of the ocean, 

 in 1868, at a meeting of the American Microscopical Society. In Jan- 

 uary, 1869, he entered more fully into a discussion of the subject before 

 the Essex Institute, at Salem, Mass. He said, 



I have been for the last fifteen years or more studying the so-called "infusorial 

 deposits" of marine origin. Among the specimens thus examined are some of the 

 rocks or shales making up the great mass of the mountains of the coast range, which 

 extend down the Pacific shore from Washington territory to the borders of Lower 

 California, and even perhaps down as far as the southernmost extremity of that penin- 

 sula. These shales are usually of a light cream color, and mainly consist of the 

 siliceous skeletons of diatomaceae and polycystina, the former being commonly con- 

 sidered as plants, the latter as animals. These are of extremely minute size, and 

 often require for their study the use of the highest magnifying powers. Many of them 

 prove to be indistinguishable from forms living at the present day on the California 

 coast. Exuding through, and often appearing at the upper portion of these rocks, to 

 which situation they have evidently been driven by heat, are found the petroleum, bitu- 

 men, and asphalt of California. Hence the state survey has conferred upon these strata 

 the name of bituminous shales. Along the Pacific coast, and lying parallel to it, are 

 islands often bearing upon their summits deposits of guano, of more or less commercial 

 value. In many cases the quantity has been small and soon removed ; but I am in- 

 formed that there are deposits of this material in that quarter of the globe still 

 unworked. At the same time, it must be remembered that the whole Pacific coast, of 



