STRUCTURE OF CORAL ISLANDS. 171 



" The reef proper extends parallel to the main range of 

 Keys, for a few miles south or south-west of it, following the 

 same curve and never receding many miles from it. The 

 distance between the reef and the main range of Keys varies 

 usually from six to two or three miles, the widest separation 

 being south of Key West, and east of the Ragged Keys, where 

 the space is about seven miles. Between this reef, upon which 

 a i^w small Keys rise at distant intervals, and the main range 

 of Keys already described, there is a broad navigable channel, 

 extending the whole range of the reef from the Marquesas to 

 Cape Florida, varying in depth from three to six fathoms ; and 

 except Love Key, where the passage is not more than fourteen 

 feet deep at low water, averaging from three to four fathoms. 

 " Further east the average depth is again the same as at 

 Love Key, but it becomes gradually more and more shoal 

 toward the east, measuring usually about two fathoms or 

 even less to the east of Long Key and Key Largo, but deep- 

 ening again somewhat toward Cape Florida, where the reef 

 converges toward the main Keys and mainland. Protected 

 by the outer reef, this channel affords a very safe navigation 

 to vessels of medium size, and would allow a secure anchor- 

 age almost everywhere throughout the whole length of the 

 reef, were the numerous deep channels which intersect the 

 outer reef well known to navigators, and marked by a regu- 

 lar system of signals. As it is, however, the reef seems 

 to present an unbroken range of most dangerous shoal 

 grounds, upon which thousands of vessels, as well as millions 

 of property, have already been wrecked. These facts have a 

 stronger claim upon the attention of the Government, since 

 there are, as already remarked, numerous passages across the 

 reef, which might enable even the largest vessels to find 

 shelter and safe anchorage behind this threatening shallow 

 baiTier. . . . 



" The reef proper, as we have remarked above, runs almost 

 parellel to the main range of Keys from Cape Florida to the 

 western extremity of the Marquesas, where it is lost in the 

 deep. It follows, in its whole extent, the same curve as the 



