Mr. Alfred Noble used for many years a form of gaging apparatus, consisting of a box with sloping bottom, in which the mortar is worked by means of a hoe. The author has used an iron box made on this principle (Fig. 2), which has given excellent results. The box is 2 feet 7 1/2 inches long, 6 inches wide at the bottom, and at the center is 6 inches deep. The level part of the bottom is 3 inches by 6 inches, and from this level part the inclined portions of the bottom slope up toward the ends at an inclination of about 22 1/2 degrees. The sides of the box extend below these inclined planes to give a level bearing for the box when in use. It is also well to have the sides flare enough to give a width of inches at the top to prevent the hoe from becoming wedged. A " German clod hoe," which is strong and heavy, yet a trifle flexible in the blade, is used in connection with the box.
Fig. 2. mixing box.
The weighed quantities of the dry ingredients being put in the box and well mixed, the measured volume of water is added. Two minutes of hard work, in which the operator may put all his strength, is sufficient to bring the mass to plasticity if the amount of water added is correct. A return to the trowel and slab method of mixing is not likely after a trial of this simple device.
S. Bent Russell, Engineering News, Jan. 3, 1891.