301 



which some of them again emerge in considerable masses, at a di- 

 stance from the precipice. The dykes are all constructed of hori- 

 zontal prisms, which form a strong contrast with the vertical pillars 

 of the strata they intersect ; and yet, says Dr. Richardson, it is hut 

 lately that these singular productions have been noticed ; and he 

 states that he himself was the first who observed them, and gave an 

 account which was published in the Transactions of the Royal Irish 

 Academy. 



For the purpose of giving a more accurate idea of these dykes, 

 Dr. Richardson gives two views of one of them, which he had over- 

 looked at the time that his essay upon that subject was published. 



Of the strata which form the facade of the precipice, the first is 

 sixty feet in thickness, and consists of large basaltic pillars very 

 rudely formed, but generally extending from one surface of the stra- 

 tum to the other. 



The second consists of a substance red as brick, and about nine 

 feet in thickness. 



The third is above fifty feet thick, and consists of that variety of 

 basalt termed irregular prismatic, resembling in its grain the colum- 

 nar basalt, but differing in its construction ; as its prisms are small, 

 not articulated, unequal and irregular in the vertical or inclined po- 

 sition of their axes. 



The fourth is about seven feet thick, columnar but not regular, 

 generally appearing white from a covering of Byssus saxatilis, which 

 has a singular predilection for this stratum. 



The fifth is ochreous, but less red than other strata of similar con- 

 sistence ; this is very friable, and is generally covered by a coating of 



The sixth is composed of rude massy pillars, very coarsely formed, 

 ten feet long. The transition from these to the seventh Dr. Richard- 

 son compared to a hand held downwards, and dividing into separate 

 fingers ; since the rude columns of the sixth appear continued into 

 those of the seventh, without any distinct line of separation, but 

 are there found divided into neat slender pillars fifty-four feet in 

 length. 



The eighth stratum is also fifty-four feet in thickness, and consists 

 of an irregular prismatic basalt similar to the third. 



The ninth is that stratum which has attracted principal attention 

 from the beautiful assemblage of neat pillars of which it consists, 

 and which at the intersection of this stratum have been so long dis- 

 tinguished by the name of the Giant's Causeway. This stratum is 

 forty-four feet in thickness ; it first appears at its opposite extremity 

 in Portmoon Bay ; from hence it rises and culminates between Ben- 

 gore and Pleskin, with its lower edge 200 feet above the water: in its 

 descent at NofFer it composes the group of pillars called the Organ; 

 at all points wherever it is accessible it has the same grain, with the 

 same size and neatness of its prisms. 



The tenth stratum on which these pillars rest, is red as minium, 

 and makes a conspicuous figure from the brightness of its colour. 



