consideration, and no useless material must be employed, every pound of metal in the structure having a legitimate function; but, economy of material must not be quoted as an excuse for using inferior details or scamping the work in respect to strength, rigidity, or appearance.

27. In all structural work the subject of aesthetics must be duly considered; and all designs are to be made in harmony with the principles thereof, to as great an extent as the money available for the work will permit or as the environment of the structure calls for.

RIVETING.

The rivets used shall generally be seven eighths (7/8) inch in diameter, smaller ones being employed for small channel flanges and legs of angle-irons less than three and a half (3 1/2) inches wide. In very heavy work the rivet diameter should be increased to fifteen sixteenths (15/16) inch, and in certain extreme cases to one inch.

The least diameters for rivets in flanges of channels are as follows, and the greatest diameters must not exceed the same by more than one sixteenth (1/16) of an inch:

The pitch of rivets in all classes of work in the direction of the stress shall never exceed six (6) inches, or sixteen (16) times the thickness of the thinnest outside plate, nor be less than three (3) diameters of the rivet. At the ends of compression-members it shall not exceed four (4) times the diameter of the rivets, for a length equal to twice the width of the member.

When two or more thicknesses or plate are riveted together in compression-members, the outer row of rivets shall not be more than four (4) diameters from the side edge of the plate.

No rivet-hole centre shall be less than one and a half (1 1/2)