In carrying out this plan Congress met every demand of the military experts. When the plans for the fortifications were pending before the Appropriations Committee of the House every military authority, from Gen. Leonard Wood and Col. George W. Goethals down, who appeared before the committee was asked if he considered the defenses recommended as sufficient for the purposes intended, and each replied in the affirmative.
These defenses consist of large forts at each end of the canal, with field works for some 6,000 mobile troops. The defenses on the Pacific side will be somewhat stronger than those on the Atlantic side, probably for the reason that better naval protection ordinarily could be afforded to the Atlantic than to the Pacific entrance, on account of the proximity of the Atlantic Waters of the canal to American shores.
At the forts on the Atlantic side four 12-inch guns, sixteen 12-inch mortars, six 6-inch guns and four 47⁄10-inch howitzers will be mounted. The guns at this end of the canal will be distributed between Toro Point on the west side of the entrance channel and Margarita Island on the east side. There will be two big 14-inch disappearing guns at each of these points. They will be so placed as to sweep the horizon in the seaward direction, and at the same time will be able to concentrate their fire on the enemy as he steams in toward the channel entrance between the great breakwaters which cut off Limon Bay from the ocean.
At the Pacific end all of the defenses will be on the east side of the channel. They will consist of one 16-inch gun, six 14-inch guns, six 6-inch guns and eight 47⁄10-inch howitzers. There are three small islands on the east side of the Pacific entrance channel known as Naos, Perico, and Flamenco. They rise precipitously out of the water and offer ideal sites for heavy defense. A huge dump or breakwater has been built from the mainland at Balboa out to Naos Island and this, in turn, has been connected with Perico and Flamenco by large stone causeways. The great dump has made several hundred acres of available land for quartering the eight companies of coast-defense troops which will be stationed at the Pacific end of the canal. These islands are 3 miles from the mainland and their guns will completely bar the way to any hostile ships which might seek to enter the canal.
On the other side of the channel, at a distance of about 12 miles, lies the island of Taboga where the Canal Commission maintains the sanitarium for its employees. It had been suggested by some that fortifications should be planted there, but it was declared by the military authorities that the guns of Naos, Perico, and Flamenco would completely command this island and prevent a hostile nation from using it as a base of operations.
The range of the guns extends more than a mile beyond Taboga Island. The big 16-inch gun which will be mounted on Perico Island is the largest ever built. It was made at the Watervliet Arsenal. It carries a projectile weighing more than a ton for a distance of 21 miles. At 17 miles it can toss its death-dealing 2,400-pound shell at an enemy as accurately as a base-ball player throws a ball to a team-mate 17 yards away. Its projectiles are filled with powerful explosives, a single one of which in the vitals of any battleship would be enough to place it out of commission. The big guns and the mortars are intended primarily for defending the canal from attack by water. The smaller guns and howitzers would come into play when an enemy approached within a mile and would be used to repel his efforts to effect a landing. Nearly all of these howitzers may be moved from place to place to meet the needs of the field troops in case of land attack. Eight of them will be permanently stationed at Gatun Locks. There will be other field works at Gatun, Miraflores, and Pedro Miguel ready for occupancy at a moment's notice by the field troops stationed on the Isthmus. These howitzers are so located that 12 of them may be concentrated at any given point in case of danger.
The big guns of the permanent forts are all mounted on disappearing carriages so that they are exposed to fire only at the moment of discharge. The 12-inch mortars will not only play their part in defending the canal from water attack, but will be able to sweep the country on the Atlantic side as far inland as the Gatun Locks and on the Pacific side as far inland as the locks at Miraflores. They have a range of nearly 4 miles, and when loaded with shrapnel will prove a most effective weapon against field troops operating anywhere within the vicinity of the locks.
The land lying contiguous to the sea-level ends of the canal will be platted off into squares exactly as a city is laid out. Should hostile troops come upon this territory the men in the fire-control station would simply ascertain the number of the block or blocks on which they were operating, and the mortars would be so oriented as to throw their big projectiles thousands of yards into the air to fall directly on those blocks. They would, therefore, be practically as useful in land operations as in the water defense.
Every feature of the armament defending the entrance of the canal will embody the latest improvements known to military science. The carriages for the big guns have been specially designed, and were put through the most thorough and exacting tests before their adoption. The fire-control stations are said to be the last word in insuring the effective use of the guns. Determining how a big gun shall be aimed so that its projectile will hit a target 10 miles away is not an easy task. Of course, the gun can not be pointed directly at the target, since this would cause the projectile to fall far short of the enemy, and also the effect of the wind and the motion of the enemy would carry it wide of its mark. To guess the range and to secure it by experimentation would be to prevent any effective fire whatever. Therefore, it is necessary first to determine the approximate range, the motion of the enemy and the velocity of the wind.
There is an ingenious instrument known as the range finder, by which the approximate distance of the target is determined. This instrument looks something like a cross between an opera glass and a small telescope. The operator puts his eyes to the opera glass part of the range finder and locates the enemy just as one would with an ordinary pair of glasses. When he locates the hostile ship he sees two images of it. There is an adjusting screw which he turns until the two images blend together and become one. The turning of this screw automatically adjusts a scale on the instrument, and when the two images exactly coalesce the distance of the ship is registered on the scale. The operators in the fire-control station make the necessary calculations as to the effect of the wind, the motion of the enemy and other elements entering into marksmanship, and telephone the results below to the men who aim the gun.