154 BULLETIN OF THE 
speed greater than two or three miles an hour, it appears that the Gulf 
Stream may have had sufficient velocity to bring about this arrangement 
of the sands. 
It is true that the arrangement of sands at and about Nantucket 
Shoals is brought about by reciprocating currents caused by the succes- 
sive movements of the tide, while the movements effected-by such a 
stream as that which flows from the Gulf of Mexico would be more con- 
stant, or in one direction. Nevertheless, it is easy to see that variations 
in the wind cause even at present a considerable variation in the posi- 
tion of the Gulf Stream off the coast of Florida. Strong winds trans- 
verse to the surface of the current affect the flow of the superficial 
waters, occasionally pressing them in against the shore, and again 
causing a southward-setting current next the beach line. It is quite 
possible that the variety of movements of the stream which may be 
necessary to produce an irregular topography have been brought about 
by such variations in direction and force of the wind. 
The greatest difficulty I find in accounting for the topography of the 
lake district is to explain the presence in the region of the large amount 
of sand which has been shaped into these irregular ridges and hollows. 
These sands have evidently come from the northward. It is not easy 
to imagine the way in which they could have come into the control of 
the Gulf Stream. One consideration, however, may aid us toward this 
understanding. With the northern margin of the Gulf Stream crossing 
Florida at the head of the present peninsula, its current would have 
swept against the northern shore of the Gulf of Mexico. It thus might 
have gained access to extensive deposits of sand, which had been accu- 
mulated in the shallows along that shore. These sands it might have 
borne onward until it brought them upon the Florida ridge. The ex- 
istence of a similar action is found in the movement of the sands against 
the eastern coast since the last upheaval of the peninsula. The shore 
from St. Augustine has received from the floor of the Atlantic an acces- 
sion of detritus accumulated on the beach which separates the main 
shore from the open sea. The amount of sandy matter appears equiva- 
lent to more than one twentieth of that contained in the sand-hills of 
the lake district. Within the limits of Florida this recently formed 
sand barrier has a length of about four hundred miles, and an average 
width of about three miles, and a probable average thickness of about 
one hundred feet. It is therefore equivalent to a strip having a length 
about twice as great as that of the lake district, and a rather greater 
thickness of material. As the lake district averages not more than 
