20 IOWA STUDIES IN NATURAL HISTORY 
was very staunch and seaworthy. This equipment is of such 
interest to marine naturalists that a somewhat detailed de- 
seription will be of use to anyone contemplating similar work. 
The launch is about twenty-seven feet over all. The dredging 
drum is geared to the fly-wheel shaft by cog-wheels and bicycle 
chains which can be engaged by a lever. The drum is immedi- 
ately abaft the engine and around it is wound the steel plow- 
wire rope leading to a davit attached to the starboard side of the 
boat and stayed by guy-ropes leading fore and aft. From the 
davit is hung the pulley through which the dredging wire 
passes. The great trouble heretofore has been the difficulty 
of dredging by backing the boat. When the dredge is caught 
on the bottom and a strong current is encountered there is often 
great trouble in circling around the dredge and getting it up 
without parting the wire or tripping the dredge. If the wire is 
passed over the stern and the dredge towed aft there is danger 
of the propeller striking the wire with disastrous results. 
These dangers are minimized by Mr. Henderson’s plan by 
which the dredging wire can go neither too far forward nor too 
far aft in the region of the propeller. A strong line is belayed 
to a post near the center of the forecastle deck just in front of 
the cockpit, and at the free end of this line a small pulley is 
lashed through which the dredging line, after running through 
the pulley just under the davit, is passed. This line can be 
shortened or lengthened at will by taking in or letting out at the 
post. While the dredge is down and the boat running forward 
the line is shortened, bringing the pulley end forward over the 
rail near the bend of the bows on the starboard side. This 
brings the dredge under control. If it caught on the bottom, 
the boat can circle around while still entirely under control and 
disengage, or, if necessary, trip the dredge. When the latter 
is clear of the bottom, the line is lengthened so that the pulley 
at its end comes almost directly under the pulley suspended 
from the davit allowing a direct pull on the dredge until it 
comes up high enough to be drawn inboard and its contents 
dumped and examined. The larger objects are then picked out 
and assorted while the mud, gravel, or sand is shoveled into a 
square sieve placed on the deck immediately aft of the cock- 
pit. Water is played in the sieve through a hose connected with 
