Note 96 — Chapter XI · THE WATERWAYS OF ITALY.

“Before the introduction of locks, contrivances called conches were in use to moderate the too great declivity of the rivers, and which were opened to allow vessels to pass through. These openings were 16 or 18 feet in width; a balance lever, loaded at the end, was made to turn on a pivot, and with it three hanging posts, united by an iron bar, which crossed them immediately above the sill; besides these three perpendicular hanging posts were two others, let some inches into the side walls. These five posts were all on the same face, and the spaces between them were all equal. When the balance beam turned upon its pivot, the three middle posts alone opened, and allowed the boats to pass, after which the balance beam was turned back to its former position. At a little distance was placed another balance beam, having attached to it a wide plank, to allow the lock keeper to pass over, as well as to place in the grooves of the hanging posts the small planks which served to exclude the water, by closing up the intervals; these were on the side opposed to the current, and in number sufficient to keep the water at the required level. Such gates, or contrivances for damming up the waters of a river, were in use at a very early time in Italy, and two such were constructed at Governolo, in the twelfth century, to pen up the waters of the Mincio on the side of Mantua.”—Cresy’s ‘Cyclopædia of Engineering.’