AGASSIZ: BAHAMAS. 143 



of which Bum Cay is auother summit. The eastern slope of the Tongue 

 of the Ocean is les^ steep than the western face, and the slope off Exuraa 

 is far less abrupt than that of the peaks forming Conception Island and 

 Watling Island, both of which rise abruptly from a narrow base at a 

 depth of over twelve hundred fathoms, and finally on the line from Cape 

 Cabron (Haiti) to Navidad Bank the slope is equally abrupt on the two 

 sides of the deep valley which separates these points. (Plate V. Fig. 9.) 

 A line from Acklin to Hogsty Reef (Plate V. Fig. 10) and thence to, 

 Inagua shows very abrupt slopes in the deep channel separating Acklin 

 from Hogsty (over one thousand fathoms) and that between Hogsty and 

 Inagua,* which is more than fourteen hundred fathoms deep. The ex- 

 tension of that line to the eastward of Inagua runs into over seventeen 

 hundred fathoms, and cuts somewhat diagonally across the slope of the 

 northern face of the deep channel to the north of Haiti. 



There are unfortunately no soundings on the Atlantic face of the 

 lines between Crooked Island Bank, Mariguana, the Caicos, Turk's Isl- 

 ands, Mouchoir, Silver, and Navidad Banks, to show definitely how far 

 these banks are separate elevations, or how many may be connected 

 together. (See Plates I. and VIII.) On the western slope the soimdings 

 seem to indicate that Turk's Islands and the banks to the eastward may 

 be the summit of a greater bank connecting them all, and that Mari- 

 guana, Plana Cays, and Caicos and Crooked Island Banks are the summits 

 of distinct banks separated by deep channels, much as Crooked Island 

 Bank is separated from Long Island by the Crooked Island Passage, with 

 nearly thirteen hundred fathoms in the deepest part. But perhaps the 

 Plana Cays, Mariguana, the Turk's Islands, and the other banks may 

 hold to one another much the same relation which the Mira por vos 

 Bank summit holds to Castle Island (Plate V. Fig. 11) and the Crooked 

 Island Bank, being separated from the last by a channel of more than 

 nine hundred fathoms in depth and from Cay Verde by a channel with a 

 depth of nearly fifteen hundred fathoms. 



The soundings parallel to Turk's Islands Bank would seem to indicate a 

 deep channel of perhaps a thousand fathoms between it and the Caicos 

 Bank and the extension of the slope of Mouchoir Bank to the eastward 

 south of Turk's Islands Bank. 



We made a line of soundings to three hundred fathoms at right angles 

 to Crooked Island Bank (Plate VI. Fig. 2) about one mile south of South- 

 west Point on Fortune Island. The bottom from three to five fathoms 

 was coarse nullipore and coral sand ; at from six to fifteen fathoms it 

 became quite fine; at one hundred and eighteen it was still finer; and 



