A perch of stone work is 1 rod long, 1½ feet thick and 1 foot high, and contains 24¾ cubic feet.

A cord of stone, like a cord of wood, contains 128 cubic feet, and will make a 100 cubic feet of wall. Three bushels of lime and a cubic yard of sand are usually estimated for a cord of stone.

Stone walls are measured by the percn (24.75 cubic feet). Openings less than 3 feet wide are counted solid; over 3 feet deducted, but 18 inches are added to the running measure for each jamb built. Arches are counted solid from their spring. Corners of buildings are measured twice. Pillars less than 3 feet are counted on 3 sides as lineal, multiplied by fourth side and depth.

It is customary to measure all foundation and dimension stone by the cubic foot. Water tables and base courses by lineal feet. All sills and lintels or ashlar, by superficial feet, and no wall less than 18 inches thick.

The greatest safe load per super. foot on

Granite Piers . . . . . . . . . . . 40 tons .

Lime stone Piers . . . . . . . . 25 tons

Sand stone Piers . . . . . . . . 15 tons

Brickwork in Cement . . . . . . 3 tons

Rubble Masonry . . . . . . . . . 2 tons

Lime Concrete Foundations 2.5 tons

The height of brick or stone piers should not exceed 12 times their least thickness at base.