Laying Th Brick

1. The packet is a small wooden frame or tray upon which two rows of ten bricks each are placed on edge in such a position that the mason can put his fingers under the brick while it is upon the packet. The bricks are placed upon the packets at the car or the wagon, and are transported on the packets to the scaffold. An important feature of the packet system is the sorting of the bricks as they are placed upon the packets, brick suitable for the face of the wall being placed upon one packet, chipped bricks and bats upon another packet, etc.

2. The special scaffold is virtually a shelf or bench about 2i, feet above the platform upon which the mason stands, upon which packets of brick are placed. The mason lifts a packet of brick from the shelf and places it within easy reach upon the wall. The scaffold and the packet do away with the necessity of the mason's stooping over and picking up each brick from the floor upon which he stands, and also further economizes the mason's time in that he does not have to spend any time in selecting the kind of brick he wants.

3. The fountain trowel is a metal can shaped something like an oxford shoe. The heel is used to scoop up the mortar from the box, and the toe has a narrow opening about 4 inches long through which the mortar is poured upon the brick. The fountain trowel makes it possible to spread a much greater quantity of mortar in a given time, and also permits the use of a softer mortar, which fills the joints better—not only by running down into the unfilled joints of the course below, but also by permitting the laying of the brick with a shove which fills the joints of the course being laid.

It is claimed that by the use of these three improvements an ordinary brick mason can lay two or three times as many bricks as with the usual appliances.

CRusHING STRENGTH OF BRIDE MASONRY.

A considerable number of experiments have been made on the crushing strength of brick-masonry piers; and the results are of interest not only as showing the strength of brick masonry, but also as revealing certain laws which are more or less applicable to stone masonry. The last is particularly valuable since no experiments have ever been made upon the strength of stone masonry.

Method of Failure.

The first sign of distress of a brick pier is a snapping or popping sound. With strong cement mortar these sounds do not usually occur until after half the ultimate load has been applied; but with lime and weak cement mortar the snapping sounds occur a little before half of the ultimate load is reached. If

the piers are less than a day or two old, the snapping sounds occur much earlier than stated above.

The first sign of approaching failure is the formation of cracks in the brick opposite the end joints in the adjacent courses. With strong cement mortars, these cracks do not appear until shortly before complete failure; while with weak mortar, the cracks appear a little longer before entire collapse of the pier. As the load increases these cracks gradually widen and increase in length, and finally failure occurs by the partial crushing of some of the bricks and the further enlargement of the longitudinal cracks. The bricks break trans versely because of their irregularities of form and because of the unequal distribution of the mortar in the joints—doubtless chiefly the first.

It is interesting to note that when a small pier rests upon a larger one, or a thin wall upon a wider one, that it is the larger or wider one that fails, even though the pressure per square inch upon it may not be more than one third or one fourth of that upon the smaller section. Apparently the failure is due to the compression of that portion of the bottom section directly under the top section, thereby causing the compressed portion to shear off from the uncom pressed part of the base section.

Effect of Irregularity of Form.

Tests made with the testing machine at the U. S. Arsenal at Watertown, Mass.,* give significant evidence as to the effect of irregularities of form of the brick upon the strength of the masonry. Hard-burned common brick having a crushing strength of 18,337 lb. per sq. in. when laid with lime mortar gave masonry having a strength of 1,814 lb. per sq. in.; while face brick having a strength of only 13,925 lb. per sq. in. gave a strength of 1,941 lb. per sq. in. The quality of the brick is indicated some what by the fact that the face brick were laid with }-inch joints, and the common brick with finch. The first brick were practically 30 per cent the stronger, while the masonry was nearly 10 per cent the weaker. With Rosendale natural-cement mortar the' face brick gave 15 per cent greater strength; and with portland-cement mortar the face brick gave masonry 34 per cent stronger than the stronger common brick. In other words, the weaker but more regular brick gave the stronger masonry.