NATURAL HISTORY OF THE DIATOMACE^. 477 



dence on the Chincha islands, while engaged in the guano trade, for nearly six months. 

 Therein we find it stated that Mr. Nash was of opinion that guano was formed in the 

 way I have described ; that the anchors of vessels in that locality bring up guano from 

 the bottom of the ocean ; that " the guano is (much of it) not composed of bird dung, 

 but is composed of the mud of the ocean;" that "the composition taken from the 

 islands, called guano, is stratified, and lies in the same form it did before it was lifted 

 up from the ocean;" that "the bottom of the ocean, on the west coast of Peru, con- 

 tains vast deposits of guano. An island, during an earthquake, rose up in the bay of 

 Callao, some years since, from the sea, containing guano four feet deep, the formation 

 the same as the Chincha islands." In conclusion, he says, "the day will come when 

 the guano at these islands will be dredged up with boats like mud from our rivers and 

 harbors." And in this expectation I fully coincide with Mr. Nash. 



Sea mud has been found to yield an excellent article of fertilizer, and 

 is collected for that purpose at different points along our coast. That 

 from the harbor of Charleston, S. C, yielded to the late Prof. Bailey a 

 rich harvest of diatomaceous forms; and I have examined the same 

 material, as well as that used in Salem, Mass., for the same purpose, 

 and known as "mussel bed," and have found them both to be full of 

 microscopic forms. 



Some years since Prof. Gregory described a remarkable deposit of sand 

 from Glenshira, which he considered to be fossil, and called it post-ter- 

 tiary. It was full of the remains of diatomacese, both marine and fresh 

 water, and had been formed evidently by the ingress of the salt water of 

 the bay into a fresh water pond. Occasionally we find the bottom of 

 fresh water marshes upheaved and everted by superincumbent pressure 

 from railroads or other passage ways being built across them. Under 

 these circumstances there are often developed deposits of the remains of 

 diatomacese. I have one such specimen from Detroit, Mich. I have also 

 seen two examples of the everting, in this way, of the ancient bed of salt 

 marshes, and in both cases the remains of diatomacese are plentiful. 



The importance of a knowledge of the diatomacese to the geologist 

 has been lost sight of up to the present time ; but now that the state of 

 New Hampshire has taken the lead in this matter, it is to be hoped that 

 they will be studied, as they occur in the rocks of other localities. 



