assumed at seven-tenths of the range in yards. The actual dimensions of this rectangle at the 3000 yard range were about 35 yards in width by 55 yards in length; and at the 6000 yard range, 50 yards in width by 80 yards in length.

It remains to consider this firing from a less technical point of view.

Group Firing.-The new battery proved in every respect to be well adapted to its purpose. The smoke so far from accumulating in the galleries, as had been suggested would be the case, was blown entirely away by the rush of the air to fill the partial vacuum created in the pits by the simultaneous discharge of the four mortars. The supply, coming largely from the galleries, assures their perfect ventilation.

During the firing the galleries were occupied by several officers to note the effects of the concussion there. The sound was heavy and deep, and was prolonged by echoes and the rush of air, but it in no way would interfere with the artillery operations. None of the incandescent lamps were broken, nor were any extinguished, although this occasionally happened with ordinary lanterns. It seemed to be the general consensus of opinion that in service the firing should be restricted to simultaneous volleys from single pits, with intervals of two or three seconds between pits. Distributing the time of fall of a battery volley over a dozen seconds, will not tend to lessen the demoralizing effects on the enemy, while the concussion in the galleries will be materially reduced.

The projectiles in the air presented a novel and interesting appearance. As viewed from the battery, the first four shell moved steadily away preserving their relative positions as accurately as if at rest, and the successive discharges from the other pits followed in echelon at short intervals, until they all faded out of sight in the distance. Their arrival at the target was described by the watchmen there as no less startling than impressive.

Although the foregoing tables afford every facility for an analysis of the distribution of the impacts, they fail to impress their characteristic uniformity upon the mind; and I have therefore prepared the accompanying diagrams, to which attention is specially invited. All the points of fall are shown in their true. relative positions; and to afford a convenient standard of comparison an outline of the battery itself is superposed in its true. azimuth to the plane of fire, and with the middle point of its Journal 41.

sixteen mortars placed at the central point of impact of all the shell. Each pit and the projectiles from it have the same distinguishing symbol, so that the starting points can be easily determined.

It will be noted that at the 3000 yard range all the shell fell far within the area of the mound of the battery, which is 134 yards wide by 182 yards long; and at the 6000 yard range all but three fell within the area included by the counterscarp, which is 154 yards wide by 202 yards long. Evidently the anticipated resemblance to an old buck and ball target was realized.

To enable the probable effects upon a warship to be studied, the deck dimensions of the Royal Sovereign (built in 1892, length 380 feet, beam 75 feet) have been added to the diagrams. By tracing the lines on transparent linen and superposing them at different positions, an opinion as to the probable effect of the volley on the ship can be formed. The following summary of such a comparison is presented.

At the 3000 yard volley, the ship always lying at the central point of impact would have received 2 hits when head on; 3 hits when at right angles to the plane of fire; 2 hits in one position and 5 hits in the other when making an angle of 45 degrees with that plane. This indicates a general average of three hits, or 20 per cent of the shots fired. At one angle she would have received 7 hits, or 47 per cent of all fired. By my formula, derived from certain Japanese single mortar practice at an actual target at a range of about two miles, published in the ARTILLERY JOURNAL in 1893, the percentage of hits to be expected in this case is 25.

At the 6000 yards volley, the ship lying in the four positions above indicated would have received hit, 2 hits, 2 hits, and 1 hit respectively giving a general average of 1.5 hits, or 10 per cent of the shots fired. At one angle she would have received 4 hits, or 27 per cent. My formula, which in this case predicts 10 hits, is the following, X representing the probable percentage of hits which would be received by a warship lying at a range of R miles, at the central point of impact.

The diagrams afford the means of extending this method of analysis to any desired extent. In brief it may be said that the distribution of the projectiles at both ranges was all that could be desired. The firing has certainly demonstrated that in one of these batteries sixteen mortars may be controlled by a single

officer in a most effective manner. While in single mortar practice the wandering increases very rapidly with the range, probably as its square, this system of grouping has materially reduced the ill effects, leaving only errors of this class dependent upon its first power to be overcome. So long as sportsmen recognize that one shot-gun is worth a dozen rifles in pigeon shooting, and so long as engineers appreciate the difficult conditions which hamper the artillerist in directing mortar practice against a ship of war, so long will batteries for vertical fire be constructed upon the principles whose soundness has been confirmed by this experimental firing.

Five of these batteries have already been constructed, and many others projected. As soon as the results of this firing became known all the details, including various matters of construction, the electric lighting, the arrangements for firing by electricity, the storage of ammunition and its most ready service (in a word every device for perfecting the arrangements) were carefully revised by the Board of Engineers and made the subject of an exhaustive report. It may be well in this connection to remark that the battery at Sandy Hook often conveys an erroneous impression upon visitors, because the high level of water in the sandy soil prevented any lowering of the pits and thus compelled an abnormal amount of enbankment. Of course whenever practicable excavation and embankment will be equalized, thus largely reducing cost to say nothing of favoing concealment.

In conclusion, I may be permitted to say that this type of battery was by no means developed by accident. The considerations which determined its form were partly artillery and partly engineer; and of the two, the former predominated. One does not expend 40,000 rounds of mortar ammunition, and spend months in the trenches studying every possible means of increasing the precision of vertical fire, without having it impressed on the mind that group control must be secured before perfection can be expected. Bringing many pieces into close juxtaposition where no variation in pointing is needful, is thus one essential condition of rapid and effective service against shipping. On the other hand the enormous amount of heavy ammunition required in a sea-coast battery (1700 tons to equip a sixteen-mortar battery with 200 rounds) introduces many troublesome engineer conditions. Moreover, long years have been required to secure ballistic data desirable for determining the proper grouping of the pits. At last, however, the type stands conpleted; and it is