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Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume VIII (1888-1891)

Birge, Edward A.
List of crustacea Cladocera from Madison, Wisconsin ,   pp. 379-Plate XIII ff. PDF (7.9 MB)


Page 397

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List of Crustacea Cladocera from Miadison, Wis.
397
                         THE CONE-DREDGE.
 The dredge which I have used for collecting seems worthy of special
 description. It consists of four parts: the body, the cone, the net, and
the screw-top. The body is a cylinder of stout tin, strengthened by a
wire at each end, four inches long, and four inches in diameter. On
top of this is placed a cone of brass netting, five inches high. This is
attached below to a circle of tin so that it fits into the top of the body
like the cover of a tin pail. The bail of the body is of stout brass wire;
the ends passed through the side of the body and enlarged, and the
loop of wire shaped so as to fit within the cone and project through a
hole in its top with an eye into which the dredge-line can be fastened.
To the end of the line is attached a snap-hook larger than the hole in
the top of the cone, so that the cone can not come off the body when
in use. There are two -cones provided for my dredge, one of one-tenth
inch mesh, and the other of one-twentieth inch.
  The A inch mesh is c  rse enough unless it is desired to secure very
large forms. For ordinary shallow water collecting it is the best size.
The cone can easily be removed for work at night in the open water.
  The net is of fine cheese cloth, eighteen to twenty-two inches long,
conical, large enough at the base to slip over the dredge body, to which
it is tied. It is faced with stout muslin for a distance of two or three
inches at each end. At the smaller end it is small enough to fit the
screw-top, a tin cylinder one inch in diameter and one and one-quarter
inches in length, with a wire in one end and on the other a zinc
screw-top, such as are used on kerosene cans.
  The seam aiong one side of the net is so made as to leave a sort of a
loop in the cloth, through-whi-ch-astring-can-be-rn. fOn eend-otthis
string is tied about the dredge body; to the other end can be attached
a weight, when desired, without having the pull of the weight come on
the net.
  This dredge is very useful for collecting small animals in shallow or
weedy water. It can easily be thrown from the shore to a distance of 50
feet or more, thus permitting much more extensive collecting from
shore than does the ordinary hand net. It can be drawn through weeds
and over muddy bottoms, straining large amounts of water without
becoming filled with mud or clogged with weed. If it is desired to col-
lect from water close to the bottom without obtaining mud, a weight
fastened to the end of the cord spoken of, so as to drag behind the
dredge will caise the dredge to lift at each pull and so exclude most of
the mud, except in very deep water. If a band of cloth is fastened
about the base of the cone, leaving only the upper part free it will ad-
mit the water just above the bottom without scraping up mud. An old
rake or other irregular piece of iron fastened to the dredge-line in front
of the dredge will stir up the bottom and thus samples of bottom ani-


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