For the same reason that concrete aggregate should be graded the stone may, in fact should, be of all sizes from spalls up to the largest that can be economically handled by the plant, although actually some sizes are skipped between the spalls and the smallest "derrick stone." The stones as they come from the quarry should be roughly rectangular in shape, clean and sound, free from seams and thin edges. In practice, however, much work must usually be done upon the stones after they come onto the dam in order to meet these requirements. The quarry forces are apt to be much more concerned with their yardage of output than with the quality; then also the inspection, and acceptance or rejection, are done upon the dam. Adjacent and within reach of each derrick is the stock pile of stone, or space in which to store temporarily the stone coming from the quarry. A great number of stones on hand, and variety of size and shape, are conducive not only to more yardage of masonry built per day but "also of a better quality of work. Right here may be mentioned the supreme test of the experience and natural ability of a foreman mason: the expert picks the stone and the non-expert picks the place. In other words, the expert knows where he wants to set a stone and casts his eye over his stock pile, picking a suitable size and shape with an unhesitating accuracy often marvelous; the non-expert goes to the stock pile and puts his hooks onto any readily accessible stone and then sets about to find a place in the masonry where it will fit reasonably well. The stone on coming from the quarry may or may not be dogged so as to hang properly in the hooks for setting, so that much of that work must be done on the dam. Here again we see that the quarry foreman is more intent upon getting the stone out of the quarry. He can load this stone to send out by means of a hold too casual and hasty to be used in setting the stone in the masonry; neither is he interested in whether the stone hangs level and right side up. It is probably not practicable to do all of this work, cleaning, inspection, etc., in the quarry, but as much as is practicable should be done there. It must be remembered that the masonry progress depends on the number and efficiency of the force that can be employed on the comparatively restricted area of the dam, and if any work can be done off of the dam do it. Further, if cleaning is done on the dam that portion of the dam must be cleaned later, and also remember that a stone which is rejected on the dam has been loaded and transported to the dam in vain.

As the stone hangs in the hooks the inspector must see that it meets all requirements not only as a stone but also in connection with its proposed place in the masonry. If there is a seam through the stone open it and permit the pieces to be used if possible. Thin edges should be trimmed off with a sledge hammer. If dirty, swing the stone away from fresh work and clean it by means of a jet of water, and, if necessary, with wire brooms. See that the stone is hanging so that it will come down squarely into its bed without tipping; it may be necessary to set down the stone and move the hooks for this purpose. See that the stone is to set in the masonry on the same bed that it occupied in the quarry, i.e., irrespective of actual dimensions see that the stone is not turned up on its side or end. If the stone is too high compared with the size of its bed, split it and use the two pieces.

Roughly it may be called poor practice to use a stone that is much higher than the least horizontal dimension of its bed. The stone should be of such shape that when set the top shall not overhang the bottom to any large extent. In other words, if the sides depart from the vertical in a marked degree, the departure shall be in such direction that they can be seen from the top. The reason for this requirement will be explained later. (See Settlement of Masonry, page 96.) See whether the shape of the bottom of the stone calls for any special treatment of the mortar bed to receive it. Lastly, see that the stone is wet before lowering it to its bed. The preparation of the rock foundation has been described; equal care should be observed in connection with a masonry surface about to be built upon. It should be thoroughly cleaned by water jet and wire brooms, any laitance, inert or damaged cement removed; also any spall or stone of whatever size whose bed is broken (i.e., has been hit or jarred so that its bond with the masonry has been broken) must be taken up.

The inspector on the dam must assume for the time being that the cement is acceptable, but he should watch the mortar carefully to check as far as may be the character of the inspection at the mixer. He should notice any serious departure from proper proportions of ingredients and the character of the sand. He should also see that the mortar is well mixed and of the proper consistency, calling for more or less water as occasion requires. Any measured quantity of water per batch may require modification, according to whether the sand is wet or dry or according to weather conditions. If the batch of mortar or any portion of it stands for some time before it is used, he must see that it is kept properly tempered. Continuous tempering is not required but occasionally it should be worked over with hoes and, if necessary, water should be added to bring it to the proper consistency for use. If proper attention is paid to this feature there is very small chance, barring a freak cement, that the mortar will become unfit for use within one and a half or two hours from the time of mixing.