racts
were chosen on the flood-plains of streams whose water was fresh but whose
height was controlled by the tide. The land lying between the levels of
high and low tide was cleared, banked along the river front and on the
sides, elaborately ditched for drainage, and equipped with "trunks" or
sluices piercing the front embankment. On a frame above either end of each
trunk a door was hung on a horizontal pivot and provided with a ratchet.
When the outer door was raised above the mouth of the trunk and the inner
door was lowered, the water in the stream at high tide would sluice through
and flood the field, whereas at low tide the water pressure from the land
side would shut the door and keep the flood in. But when the elevation of
the doors was reversed the tide would be kept out and at low tide any water
collected in the ditches from rain or seepage was automatically drained
into the river. Occasional cross embankments divided the fields for greater
convenience of control. The tide-flow system had its own limitations and
handicaps. Many of the available tracts were so narrow that the cost of
embankment was very high in proportion to the area secured; and hurricanes
from oceanward sometimes raised the streams until they over-topped the
banks and broke them. If these invading waters were briny the standing crop
would be killed and the soil perhaps made useless for several years until
fresh water had leached out the salt. At many places, in fact, the water
for the routine flowing of the crop had to be inspected and the time
awaited when the stream was not brackish.

[Footnote 4: David Ramsay, _History of South Carolina_ (Charleston, 1809),
II, 201-206.]

Economy of operation required cultivation in fairly large units. Governor
Glen wrote about 1760, "They reckon thirty slaves a proper number for a
rice plantation, and to be tended by one overseer."[5] Upon the resort to
tide-flowing the scale began to increase. For example, Sir James Wright,
governor of Georgia, had in 1771 eleven plantations on the Savannah,
Ogeechee and Canoochee Rivers, employing from 33 to 72 slaves each,
the great majority of whom were working hands.[6] At the middle of the
nineteenth century the single plantation of Governor Aiken on Jehossee
Island, South Carolina, of which more will be said in another chapter, had
some seven hundred slaves of all ages.

[Footnote 5: Carroll, _Historical Collections of South Carolina_, II, 202.]

[Footnote 6: Am