HISTORY OF

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certain level, which it seldom takes more than two or three days toeffect, by means of the lock of seven gates, that of the Zna is opened,and the vessels are gradually let down a small fall, to the number ofabout twenty in an hour. At night the lock is shut. If on the fol-lowing day there is sufficient depth, the vessels keep descending throughthe lock of the Zna ; or, if not, they must remain for a day or two untilthere is a sufficient body of water collected. Having by these meansall passed into the Shlina, they proceed without interruption throughthe lake Mastino to the beginning of the Masta, where a lock hasbeen lately constructed which holds the waters of this lake in reserve.By this reservoir the navigation is so greatly facilitated, that the lock ofthe Zna being shut, and that of the Twertza open, the latter river,which was formerly almost dry during several weeks, is now generallynavigable, even in the midst of summer, within two days after thepassage of the vessels : in spring the supply of water from the melting ofthe snows is so very considerable, that the locks, both of the Twertzaand of the Zna, are open at the same time.

With respect to the navigation of the Masta, several rivulets fallinginto it are confined by locks, which being opened successively as thevessels are passing, fill the river, and render the shallows navigable; and,being again closed, hold perpetual reservoirs of water for the same pur-pose : this operation is performed five or six times in the summer. Bysome other works lately constructed, a considerable addition of waterhas been obtained; and it is expected that the Twertza will becomealways navigable, and that the lock of the Masta will only be shut for ashort time.

The boats employed on this occasion are towed by ten horses, atthe rate of ten or twelve miles a day, up the Twertza to Vifh’nei-Vo-loshok, from which place they are rowed as far as Novogorod. Eachvessel is provided with at least ten men; those which are laden withhemp require twenty-two men. At Noffiino and Bassatino they change

pilots,