This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
For the convenience of the occupants of offices above the first floor of any building, the system of mailing letters by means of a specially constructed chute connected with the mail box at the bottom, should be adopted, and location and preparation made for it during the construction. This system, which is patented, must be installed subject to the approval of the local postmaster, and all the apparatus, when erected and accepted by the Post Office department, passes under the care and control of the Government, by which the locks and boxes are authorized.
The boxes are of various sizes and patterns, and are furnished by the makers of the chutes. The chutes are required to be in removable sections, exposed to view and easily accessible, and they may be run only in the public hall or corridors of a building. The chute must be made of metal with a plate glass front, clearly marked with the insignia of the department, and when installed becomes technically a part of the government mail box below.
The requirements for support of the chutes are a continuous vertical surface 10 1/2 inches or more in width, carried from the box below to a point not less than 4 feet 6 inches above the top of the highest floor to be supplied. In front of this vertical run must be set the iron thimbles provided by the makers, 3 5/8. inches by 9 inches, the whole absolutely plumb, with no bends or offsets anywhere.
For wooden buildings a flat casing of wood may be used, or marble or other costly material may be substituted wholly or in part. This construction is generally used where the chute runs against a wall, as in Fig. 194. Where the chute runs down beside an elevator grille, or in other places where a solid back would be objectionable, two "square root" angle irons are generally used and turned so as to give an even backing, Fig. 195, the thimble in all cases being the same, and the angle irons being secured to the floor beams or other rigid support.
This preparation may be made a part of the building contract or of the mail chute contract, but will have to be done to the satisfaction and acceptance of the makers of the chutes and of the local Post Office department.
Fig. 194. Backing of Mail Chute against Wall.
Fig. 195. Backing of Mail Chute against Grille.