INFUSORIAL EARTHS. 47 



RICHMOND. Look at the earth from Richmond it is 

 a very small quantity of a marine deposit eighteen feet 

 deep, underlying the whole city of Richmond, U.S., and ex- 

 tending over an area whose limits are not known. 



ALGIERS, ORAN. Observe the beautiful discs in that 

 slide of earth from Algiers. Use the highest power that 

 the art of man has yet constructed, and hardly will you see 

 all the beauty which the finger of our God has traced on the 

 circular valves of these little Diatoms, called Coscinodiscus, 

 Actinocyclus, Arachnoidiscus, or Heliopelta. These names 

 sound hard and perplexing to beginners, but they are full of 

 meaning to any one acquainted with Greek ; and there is 

 this great advantage in such nomenclature that it is un- 

 derstood alike by scholars of all nations. The difficulty of 

 scientific names lies not in the names themselves, so much as 

 in our deficient education, which wastes the time and the 

 intellect of young ladies in acquiring accomplishments and 

 modern languages without the solid foundation of Latin 

 and Greek, which is acknowledged to be essential for men. 

 These discs, and some others most commonly mounted as 

 objects for the microscope, will be explained presently; 

 it is necessary previously to say somewhat more of the 

 Diatomaccse generally. 



And, first : They are now decidedly placed in the vege- 

 table kingdom. They are found to consist of simple cells, 

 whose membrane is so thoroughly impregnated with silex 

 (flint) that it is indestructible by those powerful acids or by 

 such heat as would totally destroy a simple cell-membrane. 

 They consist always of two valves united at the edges, like 

 a bivalve shell, and containing endochrome, like the plant- 

 cell; sometimes oil-globules, and a granular substance 

 which has been seen to circulate within. For a proper 

 understanding of this read ' Carpenter on the Microscope / 

 'Smith on British Diatomacese;' 'Pritchard's Infusoria;' 

 ' Annals of Natural History/ 1843 and 1848 ; ' Microscopic 

 Journal/ 1854. 



The markings upon the valves, and their shape and 

 position, are the distinguishing characters which decide the 

 species. 



