THE ADZING-CUTTERS.
T the Chelsea Saw-mills, where the reader has already seen the Paxton's gutters shaped out, another interesting piece of machinery was in use for these works, for the purpose of finishing planks to a certain size and thickness, called the adzing and planing machine. An adze is a tool used by carpenters to remove any unevenness in the surface of a board in a particular spot. In this piece of machinery two cutters are fixed to a revolving arm, under which the plank is made to pass; and as it does so the cutters remove a certain thickness from the whole of the surface. The arrangement of these cutters is very plainly shown in the annexed engraving. On the under-side of the same bench to which this apparatus is fixed, three planes are set, each at an angle of about 5 degrees, by which the under-side of the plank is brought to an even face, while the upper surface is operated on by the adzing-cutters, and in this manner the plank is reduced to an even thickness throughout. As it passes on it is brought between two circular saws, which are adjusted to the width which it is desired to give to the plank. It is dragged forward towards the planes and cutters by means of an endless chain, composed of open links; which chain passes over a wheel provided with projecting pegs, so arranged as to fit into the links. The plank is kept down upon the planes, and otherwise held in position, by pressure-rollers.
THE ADZING AND PLANING MACHINE.
SECTION OF COLUMN.
HE columns in the building perform three important offices. They support the roof and the galleries, and serve as pipes to convey the rain-water from the roofs. Their form, which is beautiful, both mechanically and artistically, was suggested by Mr. Barry; it is a ring, eight inches in diameter externally, the thickness varying in the different columns, according to the weights they have to support respectively. Four flat faces, about three inches wide, are added on the outside of this ring, so that when the column is in its place, they face nearly north, south, east, and west. The column may therefore be considered as a hollow tube, of the section just described, and of the same form at each end, having at its extremities horizontally projecting rings called SNUGS, through which the bolts are passed, to fasten the columns to the connecting-pieces and base-pieces. That the hollow form adopted for the columns is that best suited to obtain the greatest strength with the least amount of material has been abundantly shown by experiments, as even two straws placed in an upright position will bear a very considerable weight; it is that also seen in the structure of the bones of animals. Of these columns there are 3,300 in the whole building.