1^0 MINERALOGY OF ST ANDREW's. 



IV. Clay- Ironstone. 



The common claystone occurs in beds from an 

 inch to upwards of a foot in thickness. It con- 

 tains a few vegetable impressions. The kidney- 

 shaped sub-species, is likewise common. Both of 

 these are included in beds of slate-clay. They 

 are sometimes collected and sent to the Carron 

 Iron-works , but the quantity so procured, is 

 trifling. 



In this place, I may take the liberty of observ- 

 ing, that the closet mineralogist may indulge in 

 hypothetical speculations regarding the formation 

 of minerals ; but such conjectures will never aid 

 the cause of science, or make us acquainted with 

 the secrets of nature. I have no doubt, but that 

 Dr Hutton, upon examining a specimen of the 

 Septarium iron-ore, was gratified with the idea of 

 having found a convincing proof of the igneous 

 consolidation of fossils, and regarded his explana* 

 tion of the singular structure of that mineral as 

 the only one which approached the truth. But 

 we hesitate not to say, that had that ingenious 

 philosopher ever attended to the natural history of 

 the Septarium, — had he ever examined it in its 

 clayey bed, — completely surrounded with matter 



