Miscellaneous Intelligence. 361 



bottom consists of a white marl, resembling when brought up in 

 the dredge newly mixed plaster of Paris, and having about its 

 consistency just as it begins to set. This same bottom extends to 

 the shoi-e; and the land itself, which is low where we went on shore 

 not more than 10 to 15 inches above high water mark, is made 

 up of the same material, which feels under foot as if one were 

 treading upon a sheet of soft india rubber; of course on shore the 

 marl is drier and has the consistency of very thick dough. It ap- 

 pears to be made up of the same material as the aeolian rocks of 

 the rest of the Bahamas, only that it has become thoroughly satu- 

 rated with salt water and in that condition it crumbles readily and 

 is then triturated into fine impalpable powder almost like deep sea 

 ooze which covers the bottom of the immence bank to the west of 

 Andros. After leaving Andros we crossed the Bank again to 

 Orange Cay and followed the eastern edge of the Gulf Stream to 

 see Riding Rocks, Guin Cay and the Beminis. We then passed to 

 Great Isaac where we saw some huge masses of seolian rocks which 

 had been thrown up along the slope of the cay about 80 fathoms 

 from high water mark to a height of 20 feet. One of these masses 

 was 15' 6" X H ;/ X 6'. We then kept on to Great Stirrup Cay coast- 

 ing along the Berry Cays, crossed over to Morgan's Bluff, on east- 

 ward of Andros down to Mastic Point on the same Sound, and 

 then returned to Nassau. 



The islands of the Bahamas (as far as Turks Island) are all of 

 aeolian origin. They were formed at a time when the Banks up 

 to the 10-fathom line must have been practically one huge irreg- 

 ularly shaped mass of low land, from the beaches of which succes- 

 sive ranges of low hills, such as we still find in New Providence, 

 must have originated. After the islands were thus raised there 

 was an extensive gradual subsidence which can be estimated at 

 about 300 feet, and during this subsidence the sea has little by 

 little eaten away the aeolian lands, leaving only here and there 

 narrow strips of lands in the shape of the present islands. Inagua 

 and Little Inagua are still in the original condition in which I 

 imagine such banks as the Crooked Island Banks, Caicos Banks 

 and other parts of the Bahamas to have been ; while the process 

 of disintegration going on at the western side of Andros shows still 

 a broad island which will in time leave only the narrow eastern strip 

 of higher land (aeolian hills) on the western edge of the tongue 

 of the ocean. Such is the structure also of Salt Cay Bank which 

 owes its present shape to the same conditions as those which have 

 given the Bahamas their present configuration. My reason for 

 assigning a subsidence of 300 feet is the depth of some of the 

 deep holes which I have surveyed on the Bank and which I 

 take to be submarine blow holes or canons in the aeolian lime- 

 stone of the Bahama hills when they were at a greater elevation 

 than now. This subsidence explains satisfactorily the cause of 

 the present configuration of the Bahamas, but teaches us nothing 

 in regard to the substratum upon which the Bahamas were built. 

 The present reefs form indeed but an insignificant part of the to- 



