iSpr.] NEW-YORK MICROSCOPICAL SOCIETY, 137 



made on yesterday evening while strolling along the river bluffs, 

 observing the character of the various exposed strata. While in 

 the vicinity of the soap factory I noticed an outcrop of argilla- 

 ceous earth, which, upon an ocular examination with a small lens, 

 •suggested the possibility of its being a fossil earth. On giving it 

 the requisite treatment, I was surprised to find that it proved to 

 be a pure diatomaceous earth, and as it happens to be the first 

 of its kind and character recorded as occurring in the Southern 

 States, I hasten to announce the fact. To convey a popular idea 

 of what the substance is in an economic way, it has the following 

 uses in the industrial arts : under the common name of tripoli 

 it is used in polishing optical lenses of all kinds; next, as the basis 

 of the well-known dentifrice Sozodont; then as an adjunct to 

 nitroglycerin in making the powerful explosive called dynamite; 

 as a silverware-polishing substance known in the trade as electro- 

 silicon; and, finally, as of universal interest as material for micro- 

 scopic study and research, its value as a microscopic novelty 

 being about one dollar a pound. Incidental to the above points 

 of interest, I would mention that its occurrence adds another 

 component rock to the geological strata of Alabama, hitherto not 

 noticed or mentioned in any work treating of the geology of 

 Alabama. I have barely examined the extent of the thick- 

 ness of the stratum, but it may have a greater thickness than four 

 feet, and may likewise underlie a very wide area in the vicinity 

 of the hill where its outcrop occurs. A substance similar in its 

 nature and composition occurs in Northern Europe, and is known 

 as 'mountain meal,' and in times of scarcity of food is mixed 

 with wheat or rye and eaten as food. The mineralogical char- 

 acteristics of the substance are in its being a white clay-like sub- 

 stance, fissile, lamellar; when moistened gives off a clay-like odor 

 and adheres to the tongue; dissolves readily in the mouth, and is 

 pleasant and agreeable to the taste; its mineral composition is 

 practically pure silica; in its microscopic appearance it is a flour 

 composed of millions of minute and very elaborately sculptured 

 silicious, glassy, or transparent shells, associated also with nu- 

 merous fresh-water sponge spicules, and the absence of all other 

 •extraneous vegetable and mineral debris, such as sand grains, etc. 

 The numerous included species are similar to forms already named 

 from localities in the New England States, but an entirely new 



