S40 GEOLOGICAL APPEARANCES 



smallest. There is an evident gradation in these aggre- 

 gates. 



93. In the spot where the blast was made, the veins are so 

 numerous, as to destroy in a great measure the character of 

 stratification in the rock, and in our specimens some of the 

 pieces cut by the veins do not exhibit a stratified structure ; 

 but, about six yards farther to the eastward, there are some di- 

 stinct, and almost undivided, strata, from which we obtained 

 specimens precisely similar, in their oryctognostic characters, to 

 many of the pieces in our specimens of the veins. Among the 

 pieces of strata intersected by these veins, we found also some 

 specimens of serpentine. 



94. The lines of junction between the veins and the strata 

 are in general clearly defined, even in some veins of which 

 the breadth does not exceed the sixteenth of an inch, and the 

 angles of the pieces of strata are often sharp. However, there 

 are partial instances of gradation, by an intermixture of sub- 

 stances, along the sides of some of the veins ; and, in the small- 

 est of them, the felspar of the vein occasionally assumes the 

 appearance of a streak of red spots, upon the dark ground of 

 the stratified mass. The connexion of such streaks with the 

 compact veins was traced in a number of cases, without any 

 exception. 



95. On the south side of the river, the limestone among the 

 more entire strata is intersected by veins of felspar, which are 

 sometimes interrupted, so that pieces of the felspar appear in- 

 sulated in the surface of the rock. Both the veins and pieces 

 of felspar are very irregular in their form and outlines. These 

 appearances of the felspar resemble those of the veins in the 

 limestone strata at B. 



96. The strata of gneiss, on the same side, are in some places 

 traversed by thin veins of white calcareous spar. One of these, 



about 



I 



