306 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



having served chiefly to furnish the alkalies. The waters 

 themselves, in some of the springs at least, contain alkaline 

 carbonates, which helps to explain their solvent action on 

 the argillaceous silicate of the bricks. 



As pointed out by Daubrt'e, the resemblances between 

 these mineral species and the similar ones found in many 

 rocks extend even to minor details of crystalline form and 

 modes of association. The small geodes in many of the 

 bricks, as the writer can testify, cannot be distinguished by 

 the eye from many specimens found in amygdaloids. 



ERUPTIVE ROCKS. 



The so-called trappean rocks, chiefly doleritic, which occur 

 in the Mesozoic red sandstone of Eastern North America, and 

 are generally recognized as eruptive, occur, for the most part, 

 in great beds or sheets interstratified with the sandstone. 

 Of these, the underlying beds near the contact present clear 

 evidences of the action upon them of the molten rock; but as 

 the contact of this with the overlying sediments is more rare- 

 ly seen, the question has been raised whether these eruptive 

 masses were not contemporaneous outflows spread over the 

 sea-bottom during the deposition of the sedimentary rocks. 

 At Feltville, N. J., according to I. C. Russel, the relation of 

 the trap to the overlying beds is such as to show its poste- 

 rior origin. The igneous rock, which is hard, bluish, and crys- 

 talline, presents on its upper surface large bosses or apoph- 

 yses penetrating the overlying shale beds, which are both 

 disturbed and altered, so that near the contact they resemble 

 somewhat the trap itself. At a distance of six or eight feet 

 they are filled with small rounded masses of a greenish epi- 

 dote-like mineral, but at twenty-five or thirty feet resume their 

 normal aspect. The upper portions of the bosses of trap are 

 scoriaceous on the surface, and amygdaloidal. In some places 

 is seen what is described as a friction-breccia, irregularly in- 

 terposed, and containing zeolites and calcite. A similar ex- 

 ample was long since noticed by II. D. Rogers as occurring 

 at Lambertville, on the Delaware, where in a sandstone bed 

 near the trap have been developed short doubly-terminated 

 crystals of black tourmaline. With these the writer has 

 found specular iron, and in an overlying bed patches of epi- 

 dote. The two localities just named occur in the same area 



