29 [23] 



expressed it, the fine-grained rock contains most flint. He is, moreover, 

 of opinion that the finegrained is rather more apt to stain. There is a 

 difference of opinion, however, on these matters. An accurate chemical 

 analysis would throw light on this subject. There is also a difference of 

 opinion as to the presence and proportion of magnesia in the different 

 samples of these rocks. Some contend that the coarse crystalline marbles 

 contain most magnesia, and that none of these Baltimore marbles have 

 less than five per cent, of that alkaline earth. These are points which 

 can be alone settled by minute chemical researches. Such analysis 

 would also throw much light on their comparative durability ; since, in 

 the opinion of recent writers on this subject, the greater the proportion of 

 accidental magnesia, the more liable ihe rock is to disintegrate until it 

 reaches a quantity equivalent in proportion to the lime, and then unit'-s 

 with it to form a true dolomite or magnesian limestone ; a very durable 

 building-material, and the same which was selected, after careful research, 

 for the exterior of the new Houses of Parliament in England. 



As already remarked, iron pyrites (bi-sulphuret of iron) occurs occa- 

 sionally in these marbles, in nests, both at Worthington's and Baker's 

 quarries; see specimen 10/?. This mineral is much prone to undergo 

 chemical ciianges by the action of the oxygen of the atmosphere : the 

 sulphur passes into the state of sulphuric acid, the iron into oxide of iron, 

 forming copperas or bi-sulphate of iron, a salt easily soluble in water, 

 which is gradually removed; leaving, of course, a cavity in which water 

 may lodge and freeze, whilst at the same time the oxidation of the iron 

 spreads a disagreeable ferruginous yellow stain around the spot. For this 

 reason great cure should be, taken, in selecting marble, to reject all masses 

 contauiinated with this mineral. 



The only locality in the neighborhood of Worthington's quarries 

 where a marble of the structure of the " alum stone" was observed, is in 

 the immediate vicinity of his dwelling house ; here, for a short distance, 

 a white marble of that texture occupies the surface. Three hundred to 

 four hundred yards beyond, on Prospect Hill, at a height of two hundred 

 and twenty-one feet ,above the bed of the northwest branch of Beaver 

 Dam creek, a highly ferruginous mica slate, charged with garnets, reaches 

 the surface : tliis seems to be the boundary of tliat formation on the east. 

 This garnetiferous micaceous schist may possibly serve to define the 

 limits of the white marble formations, and may, perhaps, be the means of 

 detecting these metanifU'phic marbles elsewhere. 



One mile north of Texas, close to the railroad, is a quarry owned by 

 Chisilla Owens, and now worked by Mx. Cooper. The rock here is well 

 bedded, and may be quarried with ease ; but the beds are, for the most 

 part, thin, and there is an interlamiiiation of mica. Here the dip is to 

 the northeast, in an opposite direction fiom what it is in the Texas quar- 

 ries. There is a bed of white crystalline marble (" alum stone") m this 

 quarry, of about two to two and a half feet thick ; whether it extends of 

 uniform appearance and thickness through the hill, is not clearly i^eeii 

 in the present state of the quarries. The blocks lying in the quarry are 

 of very regular dimensions, and the surface comparatively even, but they 

 are not large, and many of the beds are interlaminated with mica; see 

 specimen No. 11. • i • i i 



In the vicinity of Texas is a quarry owned by Judge Nesbitt, which has 

 afforded some good white marble of a rather finer grain than that of most of 



