FLORIDA REKFS. 19 
havo been formed in the same manner as tlie other keys, is Ibund in the fact 
that a brig was drifted in a heavy gale half way across the Ishmd off 
French Reef. Plantation Island, Windly's Island, the upper 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 flat, 
from which, upon 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 Vitaj 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 Vitse Key between Upper and Lower Matecumbe. 
Yewfish Key, Duck Key, and the Grassy Keys, as well 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, west of Key Vaccas and 
the Boot Keys. Instead of longitudinal islands bearing east, northeast 
and w^est-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- 
