MARYLAXD GEOLOGICAL SLKVEY Ixxiii 



fossils. Above this sandstone is the diatoniaceous eartli proper. This 

 diatomaceous bed, which is about 20 feet in thickness, is greenisli-blue 

 when fresh but weathers to brown or a light but? color on long exposure 

 to the atmosphere. In the extensive jjits at Lyons Creek, where the 

 material is being worked for commerce, the transition from the green- 

 ish-blue to bulf color may be seen in the masses removed ^progressing 

 in concentric rings. In such specimens, the fresh greenish material is 

 found at the center passing gradually into the buff-colored material 

 toward the periphery. 



The low cliffs which border Chesapeake Bay south of the pier at 

 Fairhaven are composed of diatomaceous earth with a capping of 

 Columbia gravel. From Fairhaven the beds cross southern Maryland 

 in a northeast-southwest direction following the line of strike, and 

 are worked at Lyons Creek on the Patuxent and again at Popes Creek 

 on the Potomac. They may also be found at innimicrable places be- 

 tween these points in cuttings made by water-ways. North of this 

 diagonal line, extending between Fairhaven and Popes Creek, the diato- 

 maceous beds gradually rise until they rest on hilltops, while south 

 of the diagonal line, they gradually disappear below tide. 



The diatomaceous earth, on account of its porosity and compactness, 

 is used in water filters. It is reduced readily to a fine powder and 

 makes an excellent base for polishing powders. On account of its 

 porous nature, diatomaceous earth is used as an absorbent in the manu- 

 facture of dynamite, while its non-conductivity of heat makes it a 

 valuable ingredient in packing for steam boilers and pipes, and in 

 safes. This latter is the principal use to Avhich it is put. It has been 

 thought that the diatomaceous earth might be of use in certain branches 

 of pottery manufacture which require on the part of the materials 

 refractoriness and an absence of color when burned. Dr. Heinrich 

 Pies tested a sample of the diatomaceous earth from Lyons Creek at 

 cone 27 in the Deville furnace and found that the material fused to a 

 drop of brownish glass. The non-refractory character of the diato- 

 maceous earth is thus clearly demonstrated. 



The Fairhaven diatomaceous earth has been subdivided into three 

 zones, which may be characterized as follows : 



Zone 1. — At the base of the Calvert formation and lying unconform- 



