WATERPROOFING.

The emplacements in this harbor have no condensation with which to contend, excepting in very rare instances in winter, when the iron doors will at times "sweat" on the interior. So the problem of obtaining dry rooms is simplified by having percolation only to provide against.

The problem concerns two types of emplacements-(a) those with overhead earth cover and (b) those without. Water or moisture may enter from three directions-the roof, the walls, and the floor.

Concerning the first type (a), there are several emplacements on the north side of the harbor of this character. The first two were built some years ago, very hastily, under the stress of war conditions. They are of the same style, with about 10 feet of earth cover of yellow clay; and while one has remained absolutely dry, the other has leaked in every room and passage since it was built. It is not known how the back filling was done. It is very probable that the roof surface was not properly finished off and painted. The percolation is entirely through the roof. Nothing has been done to correct the trouble; several estimates have been submitted with the annual "Preservation and repair estimates," but none has been approved.

A later style of emplacement with vertical earth cover is now being built. (See Pl. II, herewith submitted.) The sketch shows plainly the construction. Three-inch book tile is laid flat on a 3-ply felt, tar, and asphalt roof, and the cover is made of fine dry sand from the neighboring hillside. The same construction was adopted at the mortar battery, with the exception that S-shaped Spanish tile was used in place of the book tile and no roofing felt was placed under it. The Spanish tile was laid on a heavy bed of mortar, over the rough concrete roof. In addition, when back filling, the tile was covered with a bed of straw; then coarse shale rock, 6 inches in depth, from the excavation of a near-by battery; after which the sand back fill proceeded. The method has proven very efficient in obtaining a dry battery. Its cost was approximately 234 cents per square foot, while the estimated cost of the book-tile method is 16 cents per square foot.

rooms.

Concerning the second type (b), those with no vertical earth cover, various experiences have been had and various treatments have been resorted to. The 6-inch rock asphalt roof was removed from one of the earlier (1896) batteries, and 6 inches of good concrete was substituted, then painted. (See Annual Report for 1901, p. 868.) The emplacements have since been dry. At another battery, where the foundations proved insecure and the masonry cracked badly, a tin roof was placed over the roof areas (see Annual Report for 1902, Appendix Z Z, p. 2474), a method which has proven ample to give good dry The roof of a battery built three years ago was painted with P. & B. paint, several-coat work. It never proved satisfactory; the oil seemed to evaporate, leaving the asphalt constituent to blow away. Moist spots appeared in the ceilings of the passage and of one room. The concrete at this battery was made from coarse broken stone, from which the screenings had been removed. It has since been considered that there was not enough fine material to make good masonry. Rubblestone in considerable quantities was also placed in the roof as well as in the walls; the concrete therefore is not wholly water-tight, but it is believed it will be made so by having an impervious roof covering. The asphalt paint was removed during the past fiscal year and

replaced with boiled linseed oil and sand, as described in the succeeding paragraph.

The roofs of all the later emplacements, as well as the tops of parapet walls, have been given a sidewalk finish, without any joints whatever, regardless of the extent of area. The surface is then given two coats of boiled linseed oil, allowing the cement to absorb all the oil it will take. The third coat consists of oil and Prince's metallic brown, and, while the paint is still wet, screened sand (No. 10 screen), carefully dried, is swept over the surface. The paint dries slowly, and when finally hard the sand has become an intimate part of the roof covering. A year's service, with considerable walking on the roofs at one battery, has proven the treatment to be an excellent one.

Little or no trouble has been experienced from dampness coming through the walls or floors. At one battery, where the side wall of a passage has a thickness of 4 feet and has a southern exposure in elevation, it is believed that water has been driven horizontally through the wall on the line of a cold joint (between two days' concreting) during heavy rainstorms. The wall has been lately treated with two coats of "Sylvester's wash."

The method of obtaining dry rooms under loading platforms has been described under the heading "Walls and roofs."

TRANSPORTING ORDNANCE.

The transportation of ordnance, gun carriages and guns, has been done on this bay by contract by the Quartermaster's Department. The gun material has been taken on barges of from 18 to 24 inches draft. The barges were beached or taken along the side of wharves to discharge the material. The outer point of the harbor, however, presented a different problem. The swell on the ocean beach at all seasons of the year has made it unsafe to attempt landings on that side of the point, while the inner side has only small rocky beaches skirting the shore, with heights of several hundreds of feet to scale before reaching ground that is in any way level. The shore on the inner side is protected somewhat from wave action by the point, but it is not protected from the dead swell, which comes in almost every day of the year. Hence one of the beaches close in to the point, with a break in the cliff line immediately back of it so that the ordnance could be taken up a gulch, was selected for the barge landings. The rocky character of the beach is illustrated by the photograph herewith transmitted.

Much blasting had to be done to remove points of rocks which were submerged at high tide, after which the contractor for the Quartermaster's Department constructed a landing cradle (or "gridiron," as he terms it), to safely beach the barge, and to prevent it from drifting laterally while being unloaded.

The cradle consists of an altar portion, two end cribs for weighing down the altar, and side guides connecting the cribs with the shore. The altar was first built. Its construction is as follows: 6 by 12 inch planks, 8 feet long, were spiked to two 6 by 12 inch sill pieces to form the floor; 12 by 12 inch timbers, 50 feet long, were then built up on this floor, two in height, to form the sides. The structure was then floated into place at low tide, was sunk by filling with rock, after which the deck was nailed on. Upon the two ends were built rock-filled timber cribs, 6 by 6 feet inside dimensions, to the height of about 10 feet. The side guides, acting as shore anchors, joined these cribs and took the thrust of the wave action. The guides were 12 by 12 inches, 60-foot