90 
feet above the marsh, to the base of the conglomerate. It 
is seen to rest upon a compaet greenish and purplish eruptive 
rock, which proves to be identical with the first melaphyr of 
Cliff Plateau and West Porphyrite Hill. It can be traced north- 
ward about one hundred feet, the contact gradually sloping 
— 
down to the level of the marsh. Its contact with the granite 
is clearly a fault with the hade and throw to the north, and 
considerable fragments of the melaphyr appear to lie along the 
fault-fraeture above the base of the conglomerate, testifying 
further to the direction of the slip. In short, we have exposed 
at this point, on the south side of the fault, the granite capped 
by conglomerate ; and several feet below this contact, on the 
north side, the first melaphyr overlain by the main body of 
conglomerate forming Great Hill. The conglomerate on the 
south is probably the first or basal bed, as indicated by its re- 
lations to the granite; and that on the north must be the 
second bed, as proved by its relations to the melaphyr. This $5 
makes the displacement equal to the combined thickness of the 4 
basal conglomerate and the first melaphyr, perhaps 75 feet in 
all. 
It is a fact, however, that the fault-fracture cannot be traced 
upward through the conglomerate ; but the conglomerate over- 
lying the granite is essentially continuous with that north of 
the fault-line ; and it would, perhaps, be best to refer all of the 
Great Hill conglomerate to the first or basal bed, regarding the 
underlying melaphyr as a lower flow than has been seen else- 
where in the western area. This view, which would dispense 
with the fault between the granite and conglomerate, derives 
further support from the fact that the basal conglomerate 
on Granite Plateau and elsewhere is erowded with the debris of 
similar melaphyr ; but it is not followed in the construction of | 
the map, simply to avoid multiplying lava-flows where the 
facts do not absolutely require it. Still another interpretation 
is consistent with all the observed facts; viz., that the con- 
glomerate belongs wholly to the second bed and that the 
sup- 
