H1, Mitchell on recent soundings in the Gulf Stream. 71 
These natural distinctions authorize us in taking up separately 
the descriptions of these approaches, and we shall proceed to do 
so briefly, commencing at Sand Key and following the profile 
southward from A to I: then commencing at the Moro and fol- 
lowing northward from a to 2 («ee table). 
Northern Approach.—Leaving Sand Key, the water deepens 
rapidly to 13 fathoms, then shoals again to 7 fathoms upon a 
coast bar or ridge parallel to the reef, and scarcely $ths of a mile 
distant from it. Seen from the deck of a ship upon a fine day 
this bar is marked by a narrow belt of pale blue-green water in 
beautiful contrast with the dark blue-black of the ocean. The 
bottom can be seen on crossing it and appears to be a pure white 
rock zn situ, strewn sparsely over with fragments of the weathered 
and brown reef rock. Two miles farther out carries us to the 
. point A, where our table for the profile commences with sixty 
five fathoms of water on a slope of one foot in thirty seven. 
The next points B and C lie upon a nearly level plain which 
terminates about twelve miles from the reefina slope of one 
oot to twenty-two. Upon this terrace numerous soundings 
were made covering about eight miles of longitude, which show 
that the formation belongs to the reef system and lies parallel 
to it. Chips of white coral rock were brought up in one of the 
casts—in all of them the hard bottom was felt by the hand. 
At what appears to be the foot of the fore slope of this terrace 
(point EK) the bottom is found to be soft mud, and a specimen 
procured proved to be of a grey color quite in contrast both as 
regards color and consistency, with that obtained above or be- 
yond. It differed from the white muds beyond, of which we 
shall hereafter speak, in possessing a granular character and re- 
taining the same when dry. It is conceived that this terrace 
was once a dry reef covered over like Sand Key with dark 
fragments of agglomerated reef rock, and that a subsequent 
submergence has caused all this loose and weathered material to 
be swept down to the foot of the fore slope. 
Between D and K, in about 300 fathoms, the swept portion of 
the Florida Reef, if not also the dase of the formation, is p 
At F, G and H the bottom is of nearly white mud, with dashes 
of red at the last named point. These muds were found to se¢ 
on drying. The mud with dashes of red is supposed to be the 
debris of a kind of coral, quite common upon the reef, which is 
spotted as if with drops of blood. These three stations seem to 
comprise another grand terrace, because at the 500 fathoms curve 
seems to be a considerable belt where a difference of a 
mile in latitude or longitude scarcely altered the soundings. If 
this is so, we must suppose that we are not yet beyond the reef 
and that the rock still underlies the material which the specimen 
cup procures, At the foot of the fore slope of this second terrace (I) 
Pe anes wih CR a Re ee ey oe a a a age ee Ay de te Sane tae re SBN RRL 
