ABSTRACT
The appearance of stone viaducts when in course of construction is striking. A timber stage, called a " gantry," is constructed on each side of the work, sufficiently wide to allow of the piers and abutments being built between. A jenny, or crane, is then placed on a movable platform extending from one stage to the other. The materials are wound up either by hand or steam power, and are then moved slowly along till they can be lowered to the exact position they are to occupy. As soon as the
masonry is built up to the level of the gantry, a fresh lift of timber is put on, the crane is raised to the new height, and so the work is continued to another stage. By these means stones of great size can be used.
