4 
THE GEOLOGIST. 
author's idea being that the bed of Basalt forming the Causeway ex- 
tended eastward to Portmoon, a distance of two-miles (page 46), and 
that the whole of the strata are parallel to each other. These sup- 
positions are, as far as I am aware of, adopted by all subsequent 
writers on the Causeway ; and as they are errors, a transcript of my 
notes may not be unacceptable to the readers of the " Geologist ;" 
they tend at least to illustrate more fully the structure of the Basaltic 
deposits to which I allude, and are a few additional facts added to 
our present information on this interesting subject. 
Proceeding to the Causeway from Portrush, when we arrrive 
at Dunluce Castle the views of the coast are remarkably 
striking and instructive. That to the west, from a window in 
Dunluce Castle (Fig. 1) shows the junction of the Basalt and Chalk 
Lign. 1. — View looking west, from a window in Dunluce Castle. Chalk Cliffs capped by Basalt. 
most admirably. The Basalt, which for the height of some hxmdreds 
of feet above the Chalk is quite amorphous, is seen capping all the 
low chalk promontaries along the coast. Between Portrush strand 
and the stream adjoining Dunluce Castle on the west, the absolute 
junction of the two rocks can be closely studied in many places on 
the road which passes over the cliffs alluded to, the surface of the 
chalk on which the basalt rests being very uneven, and in some places 
excavated into wide and deep gullies like the transverse sections of 
river-courses ; at others it presents bluffs or possibly headlands 
against which the basalt has flowed, and wliich it eventually com- 
pletely overlays. In this view the chff close to the spectator is 
