359 



is found in order of time to have its source in the under 

 zones of the M. Lias, such as the Margaritatus and Ga^Jricornus 

 Beds, and the Spinatus ferruginous matter was doubtless drawn 

 from the same origin, but in a less marked degree. There is 

 comparatively a smaller quantity of iron-ore in the Spinatus 

 beds, but still a very perceptible quantity that came, like that 

 of the under zones, from the prodigiously lavish vegetation of 

 the ancient seas. Besides examining the rocks of the Spinatus 

 Zone by the dry way of procedure, they were also submitted to 

 the wet process. A small portion of the powdered substance 

 obtained as before described, was tested by boiling in hydro- 

 chloric acid, washing out the acid and drying the powder. 

 Looked into with the lens, and also within the field of a low 

 objective, a portion of the basis of the rock was clearly shown, 

 consisting of small white grains of a fine glassy quartz, the 

 fine glassy variety called hyalite, and the yellow colour of its 

 associated particles we infer was that of the iron film coating 

 these quartz grains, and the particles of kaolin from the broken 

 up alkaline felspars, so that this, with the particles of white 

 mica spangling in the rock yield to demonstration the complete 

 elements of a granite rock. And we would add, that the fine 

 character of the grain of a sandstone, according to the best 

 hydrographers, is dependent on situation. In our case, subject 

 to this ruling, the stone would be that formed on the low tidal 

 level of a coast line and in the sheltered recesses of a cove or 

 bay. We conclude then that from mineral evidence alone, these 

 sandstones were the product of the destructive agency of the 

 liassic sea, exerted in a creek or bay of the sea-shore upon 

 granitic rocks or their derivatives. The corroboration of this 

 result will, if necessary, be given in the section on the 

 palseontology of the zone. It is not unworthy of notice, that 

 the recent deposits on the coasts of the Anglo-French basin 

 both in shore and more to the open sea, partake of this 

 character of our Spinatus sandstone, inclining to an absence of 

 the hornblendic element, and the presence of comminuted hyaline 

 quartz, and white mica, with black mica only occasionally. Also 

 the usual felspathic residuum of clays, separated from the sands 



