marked by culverts and arches of solid masonry, and its line may be observed at a distance by white stone towers, about fifteen feet in height, placed at intervals of a mile. These are ventilators of the aqueduct ; some of them are quite ornamental, as in the case of the one at Sing Sing, others are simple round towers, and every third one has a square base, with a door by which a person may enter the aqueduct. At the top of each is an iron screen, to prevent substances from being cast into the

THE HUDSON.

ventilators. Our little group shows the different forms of these towers, which present a feature in the landscape on the eastern shore of the river, to voyagers on the Hudson. (This great work was completeil, and the water opened to the use of the inhabitants of New York, in the autumn of 1842. Its cost was about $12,000,000._) We shall meet with it frequently in our future tour towards the city.

The "High Bridge " over the Croton, at the old head of the navigation, was a wooden, rickety structure, destined soon to fall in disuse and absolute decay, because of a substantial new bridge, then being

~~_ iijiiifiji-

\EIsTIL\10ES.

constructed across the head of the bay, almost a mile below, by which the route from Croton to Sing Sing would be much shortened. Here was the "Croton Bridge" of revolutionary times, frequently mentioned in connection with military movements between New York and the Highlands ; and here is now the scene of most important experiments in the production of malleable iron from the ore, by a simple process, which, if successful, would produce a marked change in the iron manufacture. It is a process of deoxidizing iron ore in a heated hollow screw, out of which, when the process is completed, it drops into the furnace, avoids all fluxes, and comes out "blooms" of the finest iron.