MINERAL PRODUCTS. 181 



white sandstone is usually a good workable freestone, but where the 

 dyke passes through it, is so much indurated as to be unfit for masonry, 

 and is only employed for embankments and similar purposes. In Kildale, 

 the action of heat upon the contiguous shale seems to be plainly dis- 

 cernible ; part of it has been quite bleached, perhaps converted into 

 sulphate of alumine ; in other parts it has the aspect of scoria, and the 

 iron appears as a loose yellow ochre." * A white indurated earth in some 

 places separates the dyke from the neighbouring strata ; and occasionally 

 the external portions of basalt are changed to a friable mass, the iron 

 oxidated, and the felspar decomposed to porcelain clay. 



To specify the most valuable mineral productions, to determine their 

 relative importance and aptitude for economical uses, and to fix the 

 principles which should guide adventurers in quest of them, is the 

 pleasing duty of a practical geologist. No part of England enjoys 

 greater advantages from the variety and value of its subterranean 

 treasures than Yorkshire. Its rich mines of iron, lead, and zinc, its 

 vast collieries, and immeasurable quarries of building stone, flagstone, 

 slate, and limestone, are productive of increasing wealth and convenience 

 at home, and of inestimable benefit to the empire at large. The eastern 

 part of the county, though less distinguished in this respect than the 

 western, contains many useful minerals, and besides supporting a con- 

 siderable inland commerce, is capable of furnishing large supplies for 

 exportation. 



COAL occurs extensively in the north-eastern part of Yorkshire, in 

 the sandstone series between the gray limestone and the dogger, but 

 always in thin seams, and generally of inferior quality. The immense 

 advantages which would arise from the working of thick seams of good 

 coal, sufficiently account for the many unsuccessful attempts to discover 



' ,.... . . i , ., . i ...... I,. . i . ,i i- -.1 1. .. i . . , , , ...... . ,-.-... _.-. _ t 



1 ' i *~\ 



* Rev. Archdeacon Vernon, in a valuable communication on the Geology of Cleveland. 



