95 



Of these, zeolite, chalcedony, and calcareous spar, seem 

 to abound in the basalt of all countries, but never have 

 been noticed in unquestioned lava. The first fuses, and 

 the third calcines, in a very moderate heat; and, though 

 chalcedony be more refractory, yet exposed to a strong 

 heat, it loses its beauty,, and the delicacy it exhibits in 

 its natural state. These substances are most copiously 

 dispersed, also, through our basalts; but, as this topic 

 has already been often urged, I will pass on to sub- 

 stances, , peculiar to my own country. 



A variety of basalt, found in abundance at Portrush, 

 and the Skerrie Islands, is full of pectinites of belem- 

 nites, and, above all, of cornua ammonis: these are dis- 

 persed through the whole mass, equally abundant in the 

 interior, and on the surface. This basalt vitrifies, and 

 the marine substances, it contains, calcine, in the fire 

 of a common salt-pan; of course, never could have sus- 

 tained a volcanic heat. 



Another fact occurs, which seems decisive against the 

 volcanic origin of basalt. Some varieties of this fossil^ 

 contiguous to Portrush and the Giant's Causeway, upon 

 being broken by a sledge, discover, in their interior, xa- 

 vities, , some filled with fresh Avater; others bearing evi- 

 dent marks of having once contained it. Of these^ basalts, 

 some Avere of a different variety from that of the Giant's 

 Causeway, but' of similar grain and hardness; others were 

 precisely of the same variety, columnar, prismatic, artiau- 

 lattd, and exactly the same in grain. At ithe Causeway 



jj 2 itself. 



