B° ° K fources o f the latter; and at the end o f the canal a lock
— *— was made. 5. The natural courfe o f the Zna was Ihut up
by two locks in the town (at a and b), one o f which may
alfo ferve for a paffage. 6. A canal was dug from the Zna
to the Shlina, at the end o f which is the lock- o f the Zna.
The feveral canals are fupplied with water, and the veffels
are navigated from the Tvertza into the canal o f the Zna by
the following operation of the locks.
The locks of Klutihina, thofe o f a and b in the town, and
that o f the Zna'being ihut, the lock o f the Tvertza is opened,
and the waters o f the Zna and Shlina are conveyed through
the canal o f the Tvertza into that river, and the barks pafs
into the Zna at Vifhnei-Volofhok. When a fufficient number
have been admitted, the lock of the Tvertza is ihut •
and the waters being raifed to a certain level (which feldom
takes more than two or three days), by means o f the lock of
feven gates, that o f the Zna is opened; and the barks are
gradually let down a fmall fall to the number o f about twenty
in an hour. At night the lock is ihut. If on the following
day there is fufficient depth, the barks continue defcending
through the lock of the Zna ; or, i f not, they muft remain
for a day or two until there is a fufficient body o f water col-
lefted. Having by thefe means all palled into the Shlina, they
proceed, without interruption, through the lake Maftino to
the beginning o f the Mafia, where a lock has been lately
conflrucled, which holds the waters of this lake in referve.
By this refervoir the navigation is fo greatly facilitated,
that the lock o f the Zna being ihut and that of the Tvertza
open, the latter river, which was formerly almoft dry during
feveral weeks, is now generally navigable, even in the midit
o f fummer, within two days after the paffage o f the barks: in
1 ■ fpring,
fpring, the fupply o f water from the melting o f the fnows is c^ p‘
fo confiderable, that "the locks both o f the Tvertza and o f th e 1— |— i
Zna are open at the fame time.
With refpedt to the navigation o f the Mafia, feveral rivulets
falling into it are confined by. locks, which, being opened
fucceflively as the barks are paffing, fill the river, and render
the ihallows navigable ; and, being again clofed, hold perpetual
refer voirs o f water for the fame purpofe : this operation
is performed five or fix times in the fummer. By
fome other works lately conitructed, a confiderable addition
of water has been obtained ; and it is expeftecl, that the
Tvertza will become always navigable, and that the lock o f
the Mafia will only be ihut for a fhort time.
The boats employed on this occafion are towed by ten
horfes up the Tvertza to Vifhnèi-Voloihok, between ten and
twelve miles a day ; from which place they are rowed as
far as Novogorod. Each bark is provided with at leafl ten
men ; thofe which are laden with hemp require twenty-
two. At Noihino and Baflatino they change pilots, .and take
in ten additional men to pafs the upper and fmall catara£ls.
At Apezenfkoi Radok, which ftands at the head o f the great
cataracts, they procure another pilot and two aififlants ; and,
on account o f the rapidity o f the current, increafe their complement
generally to fixty men. The fall o f the river is
122-i yards perpendicular in twenty miles ; and the itream
is fo violent, that the boats not unfrequently fhoot along this
fpace within-the hour: but thèy are fometimes daihed
again ft the rocks, or overfet by accident : in the. year 17 78
above thirty were loft.
From the foot of thé great cataracts the pilot o f Vifhnèi-
Voloihok fleers the bark 120 miles further down feveral
fhoals,