I 



Mineralogy of the redhead. 359 



whence the cementing matter been derived ? The 

 origin of the former, is easily ascertained, as they 

 consist of water-worn fragments of the ancient 

 strata. The cementing matter of the conglomeratCj^ 

 is in some cases calcareous-spar ; but in general the 

 larger balls rest in a basis, consisting of minute 

 grains of quartz and felspar, without any cement 

 visible to the naked eye. The cohesion in this 

 case, may be owing to disseminated, clayey, or 

 ferruginous matter, with which the water may 

 have been charged during the period of deposi- 

 tion, assisted by the great pressure to which the 

 materials must have been subjected, both from 

 the superincumbent mass of water, and the weight 

 of the materials of the superior strata. That the 

 waters, during the deposition of this portion of the 

 floetz class, were charged with ferruginous matter, 

 is evident from the colour w^liich characterises the 

 formation, in whatever quarter of the globe it has 

 been discovered, and Vv'hich is not generally ob- 

 served in the sandstone of any subsequent period. 

 The quantity of clayey marl, which forms the 

 basis of many of the strata of sandstone, may be 

 regarded as in its original state, and may be view- 

 ed as bearing the same relation to the grains of 

 sand and gravel, as com^pact limestone does to the 

 animal relics which it encloses. The sand and 

 organic remains, must be considered as mechanical 

 deposits, the former unaltered, the latter changed 

 by the mysterious process of lapidification. 



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