Since that time these angles have been used with some modifications at a considerable number of plants, and always, to the best of my knowledge, with entire satisfaction and success. Modifications have been made in some cases. The portion of the angles built into the brickwork has sometimes been made long enough to go entirely through the brickwork, and the outer end turned up into a hook, this being imbedded in concrete poured around the lining at the top of the furnace. I have never seen any tendency for these angles to work out of the brickwork which would necessitate this additional expense.

There is, however, a very simple method of preventing this, if such danger were anticipated, by a simpler and less expensive means. The leg of the angles built into the brickwork can be sheared to approximately the taper which will make them lie to the circle of the furnace, and the portion of the angle built into the brickwork, having its largest end out, would be absolutely prevented from working forward into the furnace. If the sides of the plates before bending were sheared to an unbroken straight line this would result in slight gaps between the turned-down portions or faces of the angles, but this would be a matter of no importance.

It is something of a nuisance to level up the outside courses of the brickwork so as to bring them level with the tops of these angles, when the latter do not run clear through the wall, and to avoid this difficulty bricks of different thickness may be used on the inner row where the angles are laid. By using what firebrick makers call the standard thickness of brick (2 1/2 in.) in the courses on which the angles are to come, and the three-inch thickness in the rear courses behind them, the thickness of a 5/8-inch angle is almost compensated with a minimum of difficulty in leveling up and without using any but standard material.

There are no patents on the use of these angles made of wrought iron or mild steel, though a patent on their use when made of hard steel is held by Mr. E. B. Cook.

Another type of metal protection for the top of the furnace is one designed by Messrs. Albert Broden, manager of the Reading Iron Company, and Frank C. Roberts of Philadelphia. This is shown by Fig. 169 and consists of a cast-steel sleeve the shape and size of the furnace itself at the stock line, which rests on cast-steel brackets securely riveted to the shell.

The downcomer opening is cast through this sleeve and all brickwork is left out between it and the shell of the furnace proper. Large openings are cut through the shell to render the sleeve accessible for expansion and to provide air-cooling for it. Water troughs are cast in its outer surface and provision made for a spray pipe around the top so that a continual trickle of water may be kept up over its surface in case of necessity.

The bottom section is cast separately and is cooled by water pipes cast in. This projects down inside the top of the brickwork and protects the upper edge of the latter from the abrasion of the stock. The cooling water is trapped from the pockets in the back of the brackets, which are fastened water-tight to the shell and so prevent any possibility of water getting down through the brickwork. The joint with the hopper at the top is made by a single layer of brick laid in the usual way. This is an excellent construction and has given good results since it was put into service a short time ago. The only objection to it is the expense; being made of steel castings with accurately machined joints at all points where the different portions come together, it is a very expensive arrangement.