MARYLAND GEOLOGICAL SURVEY 211 



Eder. The exposure at this point, as already described, consists of 

 three types of clay, of which the red fire-clay is the lowest. The 

 tests made by Professor Pies show the clay to slake comparatively 

 slowly and to have a moderate air-shrinkage and low tensile strength 

 with good fire-resistance. At a temperature of about 3,000 degrees 

 the clay had not become viscous but still appeared vitrified. Plastic 

 clay from the Thomas farm and a residual refractory clay from 

 Gray's Perry, Pennsylvania, are also found in the mixture used by 

 Mr. Cowden. The clays used by the Wakefield Eire Brick Com- 

 pany are obtained from land either owned or leased by them. Sev- 

 eral varieties are used and mixed in proportions suitable for the 

 desired product. There are other good outcrops of fire-clay on the 

 property of Mr. J. H. Ford near Northeast. While the exposure at 

 this point is not very large, the clay is similar to many of the same 

 horizon which are exposed at other points, and its character is there- 

 fore of interest. The tests made upon it show that it is fairly plastic 

 and that it slakes rather slowly in water. At a temperature of 2,246 

 degrees (cone 5) it burns white and is moderately hard. It doe's not 

 vitrify, however, until heated to more than 3,000 degrees (cone 30) 

 and consequently is a clay of excellent refractoriness. 



Eire-clays have been found on Elk Neck, but they have never 

 been worked to any extent with the exception of the deposit at Hance 

 Point already mentioned. Possibly the best occurrence of fire-clay 

 in this area is that near McKinneytown. This clay, however, must 

 be hauled three miles to Northeast, or two miles and a half to North- 

 east River. 



Kaolhst. 



The kaolin deposits of Cecil county are a continuation of those 

 of Delaware that have been so extensively drawn on in the manufac- 

 ture of white ware. The material is really a residual clay derived 

 from feldspathic gneisses comparatively free from minerals contain- 

 ing iron. It is therefore white, or nearly so, and burns to a pure 

 white after it has been washed free from any impurities. Up to the 

 present time the kaolin industry of Cecil county has not proceeded 



