142 THE MIXEEAL KESOUKCES OF PKIXCE GEOKGe's COUXTY 



the lime forms only a small part of the deposit, bitt in others the 

 amount of lime exceeds 00 per cent. Experiments show that better 

 results have been obtained by the use of shell marl than by that of 

 burned stone lime. The marl acts both chemically and physically 

 and has a beneficial effect on both clayey and sandy soils. So far 

 as knoAvn. the shell marls of this region have not been utilized, 

 although they are well developed in many localities in the southern 

 part of the county. 



the diatomaceous earth. 



The principal workings of diatomaceous earth are at Lyons Creek, 

 on the Anne Artmdel side of the Patuxent River, although a bed of 

 the material occurring at the base of the Calvert formation extends 

 entirely across the southeastern portion of the county. Diatomaceous 

 earth, on account of its porosity and comj)actness, is tised in water 

 filters and as an absorbent in the manufacture of dynamite. It is 

 reduced readily to a fine powder and makes an excellent base for 

 polishing compounds, while its noncondtictivity of heat makes it a 

 valuable ingredient in packing for steam boilers and pipes and iu 

 the manufacture of safes, the latter being the principal use to which 

 it is put. It has been thought that this earth might be of use in 

 certain branches of pottery manufacture which require refractory 

 materials that have no color when burned. Heinrich Eies tested a 

 sample of diatomaceous earth from Lyons Creek at cone 27 in the 

 Deville furnace and found that the material fused to a drop of 

 brownish glass. Its nonrefractory character is thus clearly demon- 

 strated. 



the irox ore. 



The Arundel formation in Maryland has long been known as the 

 important iron-bearing member of the Potomac group and many 

 mines have been worked in this fonnation in Prince George's, Anne 

 Arundel and Baltimore cotmties. In colonial times these mines were 

 of the greatest importance and many of the cannon used in the Revo- 

 lution Avere made from Potomac iron ores. In recent vears, how- 



