64 
The contact is very sharply defined, and most admirably 
exposed; and it is conformable to the flow-structure in the 
melaphyr, dipping south-southeast 5°-10°. This melaphyr 
appears to be identical with that north of the fault, the amyg- 
dules and flow-structure being even more pronounced ; and they 
may be fairly regarded as parts of the same flow. The displace- 
ment here has been sufficient to conceal the conglomerate and 
to prevent its reappearance at the northern edge of the mela- 
phyr, perhaps fifteen fect as a minimum. It should be stated, 
however, that the melaphyr on the north or downthrow side 
appears to be about horizontal or to have a slight northerly dip. 
Above the conglomerate, on the south side of the fault, the 
melaphyr has а breadth aeross the strike before we come to the 
overlying conglomerate of nearly one hundred feet and an appar- 
ent thickness of less than twenty feet. The true thickness, how- 
ever, is próbably not less than twenty-five or thirty feet, the 
apparent diminution being due to faults with the downthrow 
to the south accompanying dikes 29 and 31.  Southwesterly or 
parallel with the railroad the sloping edge of the melaphyr flow 
is exposed broadly and almost continuously as far as dike 35. 
Near the railroad this dike marks the contact of the melaphyr 
and overlying conglomerate. The exposure is not very satis- 
factory ; but there seems no reason to doubt that the melaphyr 
passes under the conglomerate conformably and without appre- 
ciable faulting. Following the contact to the northeast, it 
sweeps around in a curve concave toward the melaphyr. The 
two rocks are seen near together, but not in actual contact, un- 
til we come to the large inclined dike (31). Here a slight 
fault with the upthrow to the north brings the melaphyr into 
sight directly under the conglomerate (Fig. 6). 
This conglomerate overlying the melaphyr is similar to that 
underlying it. It is, however, coarser and more irregular in 
composition, containing many rounded pebbles of granite and 
felsite 6 to 12 inches in diameter; and it is especially distin- 
guished by holding many large pebbles of melaphyr, some of 
which are coarsely amygdaloidal and apparently identical with 
