PRESIDENTIAL ADDRESS. 3 



its base by dragging a six foot trawl or dredge by a line let 

 down from the apex of the monument, strikes one as prepos- 

 terous. Yet the monument is less than one hundred fathoms 

 high. Multiply this height ten or fifteen times and the idea 

 seems, if possible, still more unreasonable, yet it is a fact that 

 successful dredging has been done from a height above the sea- 

 bottom of not less than twenty-five times the height of the 

 Washington monument. Living animals have been secured 

 from a depth equalling the distance from the Capitol to Rock 

 Creek, or from the Washington monument to the mansion at 

 Arlington, that is to say about two and a half miles. 



It is therefore evident that in speaking of dredging, we must 

 revise our terms and define them so as to conform more nearly 

 to the new conditions under which such work is done. 



The waters immediately adjacent to the shores were long 

 ago divided by Forbes and other pioneers in marine exploration 

 into zones or areas according to the conditions characterizing 

 them ; as, for instance, the Laminarian zone or region of brown 

 kelp, the Coralline zone or region of stony algge, &c. But for 

 general purposes and to contrast the areas of the whole sea, 

 one with another according to their chief characteristics, we 

 may now divide the entire sea bottom into three regions. 



The first is that to which light can penetrate and therefore 

 where marine vegetation can exist. This is the Litoral region 

 and in a general way, modified by especial conditions at par- 

 ticular places, it may be regarded as extending from the actual 

 shore out to the limit of one hundred fathoms. Beyond this it 

 is practically certain that no light reaches the bottom of the 

 sea and no sea weeds grow. Outside of this the borders of the 

 continents slope gradually to the bottom of the ocean, which 

 is found usually at a depth of about 2,500 fathoms. 



On the upper parts of these continental slopes the conditions 



