( ^ ) 



J Short Sketch of the Geolog^y of Nitlisdale^ chiejly in an Eco- 

 nomical Point of View, and contrasted with that of the Neigli- 

 touring Valleys. By James Stewart Menteath, Esq. 

 Younger of Closeburn, Member of the Wernerian Natural 

 History Society. (Concluded from page 323 of last Number). 



X HE strata of the limeworks at Closeburn, are divided by the 

 workmen into upper and lower posts ; and, in considering them, 

 it may not be improper to retain these names. 



The upper post of limestone is 14 feet thick, being contained 

 l^etween two impure strata of limestone, called by the workmen 

 dogger. The lower post is about 18 feet thick. The upper 

 post, with strata of sandstone and clay, overlies the lower post. 

 Both these two posts of limestone seem, from appearances, to 

 extend from the present workings of Closeburn across the 

 southern end of the Basin of Closeburn to Barjarg, on the 

 west side of the Nith. But the uniformity of their continued 

 inclination is interrupted by a throw-down or dislocation of the 

 strata. This is to be observed at the New Kiln, situated at the 

 south-west of the present workings. 



In consequence of the great expence of removing the cover 

 from the upper post of limestone, and likewise from a quantity 

 of magnesia which it contains, little of this post is used. About 

 forty years ago, specimens of this, and of the lower post, were 

 analysed by the late celebrated Dr Black of Edinburgh ; but 

 from the imperfect method of analysis then known, the presence 

 of magnesia was not detected in the upper post. But when this 

 upper post was analysed a few years ago by the late ingenious 

 Dr Murray, it was found to contain in 100 parts, 42 parts of 

 carbonate of magnesia, and 54 of carbonate of lime. When it 

 is calcined, it makes an excellent cement. 



Occasionally in this upper post cavities are observed, and are 

 often found filled with the black oxide of manganese. 



The lower post is nearly 18 feet below the upper, and sepa- 

 rated from it by strata of sandstone and clay, having, however, 

 the same dip as the upper. It is about 18 feet thick, and is 

 the pure carbonate of lime, ascertained by Dr Murray's analysis 

 to consist in 100 parts of 91 of carbonate of lime, equivalent 



