72 H. Mitchell on recent soundings in the Gulf Stream. 
tn 794 fathoms, the mud is again grey and granular while the next 
station beyond is of the ordinary white tinged with red. 
Do these features belong to the history of the Gulf Stream 
or to the geology of the coral reef? As these slopes and terra- 
ces are now scarcely traversed by the streams, we are inclined to 
regard them as exhibiting the order in which, through succes- 
sive ages, the reef has alternately subsided and stood still. As 
far as the swept portion of the reef apron extends, we see no 
indications of any caving down of the structure; and in the 
neighborhood of the second terrace the presence of mud forbids 
the supposition of long continued abrasion. 
Sou Approach.—The Moro Rock is nearly perpendicular 
at the water line but retreats at points higher up. Its northwest 
profile is convex with a mean dip of 45° from the castle wall to 
the sea. Leaving this rock and advancing 1$ miles northward, 
the bottom declines 1 foot in 7 to point a, where the depth is 
243 fathoms and the bottom, rock. From a to 6} the depth in- 
creases very rapidly, 1 foot in 6, and the foot of the Moro 
is passed. The bottom at dis a reddish brown mud which be 
coines in part granular on drying—in many respects it resembles 
the specimens from the foot of the fore slope of the coral terrace on 
the north bank of the straits. It is no doubt weathered debris 
swept down from the Moro. 
The dip of the rocky part of this space between a and d is 
unquestionably much more precipitious than the mean we have 
stated, because 1 foot in 6 is altogether too great an inclination 
for the material found at d. 
yond 6 the slope is gradual, 1 foot in 32, and terminates at 
¢ in the nearly horizontal bed of a depression which we shall 
call the Moro Channel. Here at c the depth is 748 fathoms. 
Six miles farther carries us across the Moro Channel and we 
find the depth a trifle more shallow, 710 fathoms, at d. 
Ateand / we find ourselves near the summit of a submarine 
mountain whose height above the bed of the Straits is about 
twenty four hundred feet. This mountain, lying but a few miles 
to the northward of the axis of the Gulf Stream, may be claimed 
as a point of decided interest in this survey. It is scarcely 
twenty one miles from the shore of Cuba whose hills are in fall 
view if the weather is fine. Six casts were made upon its sam- 
a specimen and observed the temperature to be 60° 
