THE ISLE OF EIGG. 149 



of Eigg, we shall next, in the same way, examine those un- 

 stratified or Plutonic masses which are connected with 

 them. The igneous rocks, which form the most of this 

 island, belong to the trap family ; they are composed of 

 augite and felspar, and constitute all that part of the island 

 to the south of a line extending from Kildonan on the east 

 to the opposite shore at Laig ; while, to the north of this 

 boundary, the trap rests upon the oolitic strata which we 

 have just noticed. The most usual manner in which the 

 trap is connected with the sandstone, limestone, and shale, 

 is as veins which run parallel to the almost horizontal 

 strata, many of which indeed conform so strictly to the 

 aqueous deposits, that, if the mere form of the mass with- 

 in a limited extent be alone considered, an observer might 

 imagine them as examples of true stratification. On pro- 

 secuting the examination of these masses (filons couches) 

 farther, it will, in almost every instance, be found that all 

 depart from their parallelism, and either cross the upper 

 or lower strata ; or if the bed-like masses continue their 

 course, they send off smaller veinous bodies which ramify 

 into the sandstone. 



In regard to the trap, which alternates with the several 

 Neptunian deposits, relatively to the trap-rocks lying south- 

 wards of the line we have referred to, it must be remarked, 

 that a thick covering of alluvial matter prevents us from 

 arriving at any perfect knowledge. That it is connected at 

 one extremity with a central body, can, we imagine, never 

 be doubted, as it is supported by phenomena observable in 

 other quarters, where similar masses, alternating and run- 

 ning parallel with stratified rocks, may be examined 

 throughout their whole extent. Besides the parallelly in- 

 truding veins of trap which traverse the strata, there are 

 others which rise more or less vertically through them 



