EGG. GEOLOGY, 511 



southern, and consequently elevated at the northern extre- 

 mity. The sea washes the foot of this rock to the southward 

 from the bay of Lagg to Balinakily, no other substance ap- 

 pearing beneath it ; nor are any strata either primary or 

 secondary to be seen throughout this whole extent. But in 

 examining the shore from the bay just mentioned round the 

 northern extremity of the island to the same point, nume- 

 rous beds of the secondary rocks are found mixed with 

 the trap; in an order sufficiently regular in a general 

 view, but so inconstant in the minuter details, that no 

 single description will apply to all the points that admit 

 of examination. As the most perfect display of these 

 strata is to be seen at the highest point of the northern 

 shore, I shall enumerate them as they occur at that 

 place ; their deficiencies and obscurities in others will be 

 the more intelligible. 



The uppermost and principal bed consists of trap/* 

 attaining the thickness of 100 feet or more, and incum- 

 bent on several strata of a white sandstone, the collective 

 depth of which appears to vary from twenty to fifty feet. 

 Below the sandstone is a second bed of trap, followed by 

 a considerable series of small strata consisting of limestone 

 alternating with an argillaceous schist that must be 

 considered as a variety of slate clay or shale. This is 

 again followed by basalt, which is succeeded by two dis- 

 tinct portions of stratified rock. The first of these is a 

 sandstone with some peculiarity of character, and the 

 next a series of thin alternating laminae of sandstone and 

 shale : the whole resting ultimately on a bed of columnar 

 basalt about fifty feet in thickness, terminating in the 

 water line ; beyond which no further information can be 

 procured, since the regular dipping of the whole mass 

 commences at this point. It is owing to this dip that the 

 uppermost sandstone, which is elevated many hundred 

 feet at the point just described, is found reaching to the 



* Plate XIX. fig. 1. Plate XXIII. fig. 5. 



