60 W. R. Hopkins on Screw-Propellors. 
cold bands, which seem inexplicable on any other theory, unless 
we suppose the existence of lateral currents, it seems to me that 
the weight of probability will strongly incline to sedimentary 
deposit as the cause also of these ridges. In fact, everything 
about the Gulf Stream seems to point to the conclusion that it 
has been the architect of its own curves, its own banks, and its 
own configuration of sea bottom. 
here is one other conclusion which, though not connected 
with any particular theory of the formation of Florida, is, never- 
theless, naturally suggested by the subject of this paper. We 
have seen that the peninsula of Florida has been progressively 
advancing towards Cuba as a fixed point, and the Gulf Stream 
as been becoming more and more narrow. If, therefore, as 1s 
probable, the quantity of water carried by the Gulf Stream has 
remained constant, it follows that the velocity with which the 
stream emerges from the Straits of Florida, and therefore the 
distance to which it penetrates the still water of the Atlantic, 
progressively increasing. Now, unless there has been 
some very remarkable change in the direction of this current, it 
necessarily follows that its warming influence upon the European 
continent has also been progressively increasing. Have we not 
here, if not a sufficient cause, at least one of the true causes of 
that great change which we know has taken place in the climate 
of Europe since the glacial period ? 
Thus we see that the advancing ppt of Florida has been pro- 
gressively warming the climate of Europe, and thus, perhaps, 
controlling the destinies of the human race. Can we conceive a 
more beautiful instance than this of that sympathy which exists 
between the most distant portions of our globe, and which binds 
all its members together in one organic whole? ‘ 
Art. IX.—On Screw-Propellors ; by W. Rogers Hopxtns, As- 
sistant Professor, U.S. Naval Academy, Annapolis. 
Is it not strange that while in heavy machinery on land re- 
volving at high velocities no difficulty is found in preventing 
heating in the journals, from friction, that few propellors are 
afloat at sea that have not suffered seriously from this cause? 
We hear of vessels on both sides of the Atlantic, mercantile and 
armed, that are retarded by the heating and wearing in the stuff 
ing boxes and bearings of their shafts 
a 
