196
N . A . HOLMF,
Hvorslev and Stetson (1946) developed a free-fall method by which
a, geological coring tube was allowed to fall freely under its own weight
(Fig. 16) for the last part of the descent, a loose bight of chain being
attached for recovery, but i t is doubtful if such a method would be
successful for biological sampling.
An attempt to increase the speed of descent of a, grab is described
Cable from ship
1
s
-
i
-.
Release __
I
FIG. 15. Free-fall core-sampler. Tho body and fine of the original model were 157 crn
long, and total weight WSB about 430 kg. (Redrawn from Hvordsv and Stetnon,
1946.) The corer may also be urntl without relearn gear by allowing the warp to
run out freely from the winrh as the corm approaches bottom.
by Lisitsen and Udintsev (1955). The grab has opening lids to the tops
of the buckets so that there is a free flow of water through the bucket8
during lowering, which can be carried out at the considerably increased
speed of 170 m/min (Figs. 16, 17). The authors claim good results
from the use of this grab in deep water, but it seems likely that the
main advantage is in the speed of lowering rather than in greatly
increased sediment penetration.
One of the disadvantages of most grabs is that the buckets are
closed by an upward pull on the wire just before they leave the bottom.
N . A . HOLMF,
Hvorslev and Stetson (1946) developed a free-fall method by which
a, geological coring tube was allowed to fall freely under its own weight
(Fig. 16) for the last part of the descent, a loose bight of chain being
attached for recovery, but i t is doubtful if such a method would be
successful for biological sampling.
An attempt to increase the speed of descent of a, grab is described
Cable from ship
1
s
-
i
-.
Release __
I
FIG. 15. Free-fall core-sampler. Tho body and fine of the original model were 157 crn
long, and total weight WSB about 430 kg. (Redrawn from Hvordsv and Stetnon,
1946.) The corer may also be urntl without relearn gear by allowing the warp to
run out freely from the winrh as the corm approaches bottom.
by Lisitsen and Udintsev (1955). The grab has opening lids to the tops
of the buckets so that there is a free flow of water through the bucket8
during lowering, which can be carried out at the considerably increased
speed of 170 m/min (Figs. 16, 17). The authors claim good results
from the use of this grab in deep water, but it seems likely that the
main advantage is in the speed of lowering rather than in greatly
increased sediment penetration.
One of the disadvantages of most grabs is that the buckets are
closed by an upward pull on the wire just before they leave the bottom.