( 475 ) 
XXVII.— iVo^?*c^ in regard to the Trap Rocks 
in the Mountain Districts of the IFest and 
North-west of the Counties of York, Durham, 
Westmoreland, Cumherla7id, and Northumber- 
land, 
By Henry With am, Esq. of Lartington. 
(Read Sd May 1824.) 
The various opinions which have been entertained at 
different periods respecting the origin of the Trap Forma- 
tion, by the most distinguished geologists, gives a pecu- 
har interest to its geognostical history, and confers on those 
districts where it occurs a high degree of importance. Some 
geologists, as is well known, maintain, that secondary trap 
rocks owe their origin to the action of subterranean heat ; 
which power, it is alleged, was instrumental in giving them 
their mineralogical characters, and present position in the 
crust of the Earth. This immeasurable power, according to 
the igneous theory, forced them from their birthplace, very 
deep in the bowels of the earth — even under gneiss and 
mica-slate, through every variety of primitive and transition 
rock, to their present place in the formations of the second- 
ary class. These secondary traps, then, if this explanation 
