FLORIDA REEFB. 19 



have been formed in the same manner as the other keys, is fonnd in the fact 

 that a brig was drifted in a heavy gale half way across the Island off 

 French Reef. Plantation Island, Windly's Island, the uj)per and lower Mate- 

 cumbe which follow Key Largo, are not so high, and are more like Elliott's 

 Key. Plantation Island is encircled to the seaward by a spreading mud fiat, 

 from which, npon an extensive spur, Key Tavernier rises to the east. The 

 others. Upper and Lower Matecumbe, as well as Long Key, Tea-table 

 Key, and Lignum Vitse Key are connected with Mangrove Keys. To the 

 seaward of the two Matecumbes, however, there are sand beaches, while In- 

 dian Key, which stands out into the ship-channel, is entirely rocky, resem- 

 bling, as already stated, the eastern shore of Key Largo. A mud flat runs 

 along the inside of all these keys, from Lower Matecumbe to the northernmost 

 extremity of Key Largo. It extends for several miles to the north of the 

 keys, and is separated from the mud flats which reach the main-land only 

 by a narrow channel varying from three to four or five feet in depth. This 

 channel is marked by dots upon the map. Another mud flat projects like 

 a spur from Lignum Vitoe Key between Upper and Lower Matecumbe. 

 Yewfish Key, Duck Key, and the Grassy Keys, as Avell as Key Vaccas, Boot 

 Key, and The Sisters, constitute a series of small low keys, mostly covered 

 by mangroves, with here and there a sand beach on the seaward side, while 

 spurs of mud flats jut out from the leaward side. The Bahia Hondas have 

 a similar appearance, but here the reef begins to change its character. 

 Indeed, the change is already marked farther east, Avest of Key Vaccas and 

 the Boot Keys. Instead of longitudinal islands bearing east, northeast 

 and west-northwest, we now have an archipelago of low islands rising 

 above extensive mud flats which are also interspersed with innumerable 

 mangrove islands crowded together in small groups, the main islands bear- 

 ing north-northwest. The principal of these islands are known as Little 

 Pine Island and Pine Island. The main channels intersecting this archi- 

 pelago run also north-northwest, between Little Pine Islands and the Bahia 

 Hondas, and between the western and eastern Pine Islands. The main 

 islands of this group are very flat, and consist of thin layers of a regularly 

 stratified and somewhat oolitical limestone, evidently formed by deposits of 

 limestone mud. The uppermost layers have evidently been solidified above 

 the level of the sea, for they present numerous cracks of shrinkage such as 

 are everywhere observed upon dry mud flats ; the edges of these fissures 

 being here and there slightly raised, and even upturned, so as to be sepa- 



