295 



At Ballycloghan, a mile and a-half north-west of Broughshane, there 

 is a protrusion of whitish fine-grained rock, which is quarried and cut 

 for window sills and other economic uses in the country. A quarry is 

 opened in it at the National Schoolhouse, and worked to the extent 

 of half an acre. The rock in this quarry is of a whitish colour and 

 very fine grain, and in this respect is totally unlike the rock of the 

 Carnearny district just spoken of, which is in a high state of crystalliza- 

 tion. It has a vertical cleavage, by which it splits into fiags from two 

 to four or six inches in thickness, and is easily worked with punch or 

 chisel. The mass in its course is generally decomposed into sand, 

 coarse or fine, and seldom in the condition of solid hard rock at the 

 surface. It appears to be a great dyke or protrusion running from the 

 quarry at Ballycloghan to Lismacrogher on the north-west, a distance 

 of about three miles. The low flattish land in which it is supposed to 

 occur, under the bog and drift, is from one-eighth to a quarter of a mile 

 wide. On both sides of this low space the black trap appears in higher 

 hummocks of rock. In this space, as the solid rock is rarely seen at the 

 surface, the line of the protrusion is traced by means of the subsoil, 

 which appears in many places to be the rock decomposed into a whitish 

 sand or gravel. 



Analysis cannot probably do much to determine what kind of rock 

 this may be. I have shown some specimens of it to an able chemical 

 friend, who, on examining it with a lens, said it is composed of the 

 debris of granite well ground down and deposited in water. It has a 

 large amount of quartz in the state of very fine sand, mixed with felspar 

 reduced to clay, and a little mica. The quartz is sometimes in fragments 

 one-eighth of an inch in diameter ; one such fragment appearing in about 

 every two inches of the rock. There appears indeed to be alternating 

 stripes of different shades of light gray and yellowish white colour, 

 like sedimentary lines, so thin as to have about ten or fifteen to the 

 inch, and those lines coincide exactly with the vertical cleavage lines — 

 if cleavage lines they be — to which I have alluded. 



This idea of its being a sedimentary rock presents a great difficulty 

 in the ease of a band of rock three miles long, and one -eighth to a 

 quarter of a mile wide, surrounded by trap on every side, and thereby 

 suggesting the idea that it came up through that trap from the depths 

 below. It might have been deposited in water in level beds in the old 

 times, then covered up with the other deposits up to the chalk and trap 

 of the country; but how were the layers of this mass changed from a 

 horizontal to a vertical position ? "Without working out this question 

 to my own satisfaction, I must leave it to more able geologists to crack 

 this nut. It is too hard for me. 



Teap. 



All geologists now believe that trap is a rock of volcanic origin. 

 The mass of which it is composed was melted in the depths of the earth 

 by subterranean heat, and in that condition it broke or was forced up 

 through the overlaying formations, was poured out, and spread over what- 

 ever foundation of other rocks happened to be in the way, as the lava 



