382 OBSEEVATIONS ON THE CUERENTS. 



can be no doubt. It has its daily and monthly variations in Veloclf-y. 

 Direction, and Temj.3rature, changing with as perfect regularity as tlie 

 tides in a harbour." 



(367.) The Gulf Stream has had from the earliest times a very bad repu- 

 tation among ship-masters for its dangerous character, and the hundr-eds 

 of wrecks and millions of property which have bestrewed its margin have 

 given good occasion for such a description. For not only is it to be dreaded 

 for its stormy nature, but also for its violent stream, which renders a sail- 

 ing vessel quite unmanageable during a calm. At these times, should hazy 

 weather occur, and the sameness of the shores mislead the stranger, he is 

 is open to many difficulties and dangers. But the excellent system of 

 beaconage along the Florida Eeefs, and the fine lights which direct by 

 night, have very much reduced its bad character, and diminished the 

 employment of that enterprising race, the wreckers of Kay West and the 

 Florida Eeefs. 



(368.) The Channel of the Gulf Stream. — The peculiar and dangerous 

 character of the shores of the Straits of Florida, and the necessity which 

 existed for the establishment of some means of averting the mischief the 

 Gulf Stream annually occasioned, led to a minute examination of its fea- 

 tures so geologically and geographically interesting, which has been made 

 practically useful by the erection of a fine line of beacons and the necessary 

 lighthouses upon the Florida Eeefs. 



Professor Agassiz, who investigated this subject, has shown that the 

 Florida Kays and Eeefs are essentially of coral formation in various stages 

 of existence. At Kay West, the basis of this is shown to be a coarse oolitic 

 rock with cross stratifications, and dipping at various angles in different 

 directions. The formation of coral upon this rock extends not only over the 

 Kays, but also to the mainland of Florida, and by a careful process of in- 

 quiry and reasoning it may be inferred that a very different order of things 

 existed at no very remote period of the world's history. 



We have a peninsula — a narrow, flat strip of land, projecting for about 

 5 degrees from the mainland, between the Atlantic Ocean and the Gulf of 

 Mexico, and forming an effective barrier between the waters of the two seas, 

 which otherwise, even by the change of a few feet in the relative level of 

 the intervening peninsula, would communicate freely with one another ; 

 and this peninsula we now know to have been added to the continent, step 

 by step, in a Southerly direction. 



We know that the time cannot be far behind us when the present reef, 

 with its few kays, did not exist, and when the channel, therefore, was 

 broader, and the Gulf Stream flowed directly along the main range of kays. 

 We know, further, that at some earlier period the kays themselves were not 

 yet formed, and that the channel between Cuba and Florida was wider still, 

 washing freely over the grounds now known as the mud-flats, between the 

 kays and the mainland, and that there was then nothing to impede a free 

 oommunication between the Gulf of Mexico and the Atlantic Ocean. 



If it is true that the Gulf Stream and the South- West winds have an in- 

 fluence in determining the course of the isothermal lines upon the two 

 sides of the Atlantic, and of raising beyond their normal altitude the mean 

 annual temperatures of North- West Europe, then we may look to the 



