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The practical interpretation of the second query, however, has no reference to the question of an exclusive defence by the forts or ships, so far as the Atlantic coast is concerned, if I understand rightly. The answer must necessarily be based upon the existing state of things; and as a great part of the contemplated system of coast fortification has been completed, the expediency of substituting ships, &c., has reference only to such of the system as remains unfinished.
The works for the protection of Boston and of the navy yard at Norfolk are already completed. At New York, likewise, excepting the fort on Sandy Hook. The approach to Philadelphia, however, and the anchorage at the breakwater are yet undefended, though the works have been planned and perhaps partly appropriated for.
I have no doubt when these places, and some harbor on the southeast coast, have received whatever aid can be furnished by the art of the engineer, that a naval force of no immoderate extent will be fully competent to defend the Atlantic seacoast from any attempts which an enemy would find it advisable to make.
Under no circumstances, except of the most unquestionable superiority at sea, is it presumed that it would be well to resort to a defence exclusively naval.
The ship and the fort have each a particular province in every general system of well regulated national defence, and if these can be agreed on the result will be reliable and economical. I do not mean to apply the latter word to the least possible outlay of means, but to the judicious expenditure of whatever may be required to effect the end proposed.
It is not needful here to enter into any statement of the part properly allotted to forts; this has been ably and frequently expounded by the chief engineer.
Admitting them fully, and the necessity also for the works in the principal points above alluded to, as the base for the naval operations that are to guard the intermediate points, it may be well to examine whether even the great harbors and watercourses are fully defensible by fortifications, when of the most extensive character.
Let us again revert to the defences of New York.
The first object is to prevent the occupation of the lower harbor by a hostile fleet, for if able to effect this the enemy would obtain the following advantages, according to the report of the board of engineers, (page 54 :)
"An enemy's squadron being in the bay, into which entrance is very easy, would set a seal upon this outlet of the harbor. Not a vessel could enter or depart at any season of the year. And it would also intercept the water communication, by way of the Raritan, between New York and Philadelphia.
“ The same squadron could land a force on the beach of Gravesend bay, (the place of the landing of the British, which brought on the battle of Long Island, in the revolutionary war,) within seven miles of the city of Brooklyn, of its commanding heights, and of the navy yard, with no intervening obstacle of any
“This danger is imminent, and it would not fail, in the event of war, to be as fully realized as it was during the last war, when, on the rumor of an expedition being in preparation in England, 27,000 militia were assembled to cover the city from an attack of this sort. It is apparent that the defences near the city and those of the Narrows, indispensable as they are for other purposes, cannot be made to prevent this enterprise.”
There can be no doubt of the great damage that would be wrought to the revenue of the government, and to the immense interests of various sections, by the presence of an enemy's force in the lower harbor. A heavy expenditure would be well laid out in establishing the means of prevention, and this should certainly be looked to in time.
What fortifications, then, can be applied to the purpose, and how far will they be efficacious in excluding a fleet?
A glance at the chart will show a wide extent of water between the outer extremes of land that form the harbor from Sandy Hook to Coney island; the distance is about seven miles. Large ships, however, are not at liberty to pass over any part of this entrance. Their course is confined to two channels, the principal one of which is near the Hook, and other somewhat to the northward of it, (the swash.) Line-of-battle ships can use the first only, but the heaviest steam frigate in our service, when loaded for a long cruise, only draws twenty feet, (the Susquehanna,) and therefore has sufficient water to pass in by the swash channel.
According to their report the board of engineers propose to fortify the east branch and middle ground, under the belief that the bottom was sufficiently permanent to receive such works. Recent surveys, however, have so far shaken such opinion as to induce them to forego the project.
The report goes on to state, (page 55:) "This may, however, be said with certainty, namely: that, all other means failing, works may be erected on Sandy Hook which will have a good action upon the channel, and under cover of which bomb ketches or steam batteries, or both, may lie. With such an arrangement there would be little probability of the lower bay being occupied as a blockading station."
I have already endeavored to make it apparent that any works on the Hook would, of themselves, be insufficient to prevent the passage of ships into the lower harbor, and it will be perceived that this is also fairly inferable from the passage just quoted, as it includes other aid in the arrangement designed to prevent the occupation of the lower harbor.
Line-of-battle ships, in taking the main channel, would, however, sustain the fire of a fort without material detriment for the eight or ten minutes required to pass it, with a fair wind and tide; and, if annoyed by the floating batteries and ketches, would not hesitate to run close to them and brush them with a few broadsides, which would probably leave them little more to do than to take care of themselves.
The heaviest steamers, by taking the swash channel, would avoid the fire of the fort and floating batteries altogether, and afterward have leisure to destroy the latter from the anchorage of the lower harbor.
So far, therefore, from believing that, “with such an arrangement, there would be little probability of the lower bay being occupied as a blockading station," it seems conclusive that the occupation of the lower harbor by a naval force would be liable to the least degree of interruption from the defences planned for that purpose. The report itself admits the necessity of using floating batteries and bomb ketches as auxiliaries, which, of all the naval means, are certainly the least worthy of reliance. With the limited preventive powers of a fort, so far as passage is concerned, they have in no degree the least of its capacity to endure battering, their material being as vulnerable as that of a ship, without its great advantage of passing from one point to another, whether far or near. And as for bomb ketches against objects no larger than ships, and those in rapid motion, it may be said that the chances of even a single bomb dropping upon them are too remote to be taken into account as a means of defence in the conditions of this case.
Conceiving, therefore, the entrance of an enemy into the lower harbor to be fairly feasible, the next matter for consideration is the capacity of the inner defences to prevent entrance into the upper harbor and the destruction of such means of war and revenue as may be found in and about the city, such as the vessels-of-war built or building at the navy yard, of the timber, ordnance, and stores, and, above all, of the extensive private establishments for manufacturing steam-engines; a purpose which, if effected, would cripple the nation in every enterprise of offence and defence, and probably could not be remedied in the course of a war.
The levying of contributions might not be disregarded where means so ample were placed by the chances of war within the grasp of an invader. These objects individually are sufficient to warrant a military attempt on a large scale.
The number and character of the works arranged by the engineers are best set forth in the language of the “Report,” page 54:
“At the Narrows, about seven miles below the city, the passage becomes so contracted as to permit good disposition to be made for defence. On the Long Island side of the Narrows is Fort Lafayette, which is a strong water battery, standing on a reef at some distance from the shore; and immediately behind it, on the top of the bank, is a small but strong work called Fort Hamilton. Some repairs being applied to these works, this position may be regarded as well occupied.
"On the west side or Staten Island side of the Narrows are the following works belonging to the State of New York, viz: Fort Richmond, which is a water battery; Battery Hudson, which is at some height above the water; Battery Morton, which is a small battery on the top of the hill; and Fort Tompkins, which is also on the top of the hill, and is the principal work. All these need great repairs, but, being once in proper order, would afford a very important contribution to the defence of the passage, nothing further indeed being contemplated for this position except the construction of a small redoubt on a commanding hill a little to the southwest. The repairs of these works cannot too soon be taken in hand, and it is hoped some arrangements may soon be made with the State authorities to that end.
With the Narrows thus defended, and the works near the city in perfect order, New York might be regarded as pretty well protected against any attack by water through this passage."
That these works are themselves perfectly capable of resisting the attack of any fleet there is no doubt, but that they are able to interdict the passage to a like naval force is very far from being certain; on the contrary, the chances of passing, without suffering to any material extent, are reasonable enough to warrant the attempt in view of the great results to be derived therefrom.
The distance between the nearest batteries is seventeen hundred yards. The water is deep to the very shore of Staten Island, and the edge of the reef well marked, on the Long Island side, by the water battery. The largest ship, therefore, may choose the course likely to be most advantageous in receiving the least weight of metal.
If the officer in command run mid-channel he will be under the fire of both sides at a most effective distance (eight hundred yards) when right abreast of them, but by taking one side or the other he will recede from one fire, and in approaching the other be exposed to no great increase of effect.
Suppose he choose to keep the left shore and risk the fire of these batteries, while, by doing so, he will place fourteen or fifteen hundred yards between his ships and the Long Island batteries.
The sketch annexed shows the course within the scope of effective fire, which is about two statute miles. It will hardly be questioned that a decent sea steamer should run ten knots hourly (sea miles) in smooth water; these are equal to eleven and a half statute miles. Of course, she takes the strength of a flood tide and spreads every stitch of canvas to a fair wind, which ought to add another mile, making the total speed twelve and a half statute miles per hour, (three hundred and sixty-seven yards per minute,) at which rate she will pass over a mile in four and three-fourth minutes.
Tracing the assigned course through the scope of the guns on both sides, marked by the circles, it will be found that the distance run is about two miles; that is, the steamer will not be more than ten minutes under fire.
The 32-pounders and the 42-pounders of the Long Island water battery will require an elevation of about three degrees to reach the enemy, the 8-inch seacoast howitzers about four degrees—both unfavorable to ricochet; for the projectiles will bound high in rising, and with a power much diminished even when the weather is smooth ; but with the ripple occasioned by the moderate breeze, which is supposed to be taken advantage of, the ricochet could not be depended on for direction or force, and therefore the direct firing only will be available on the right hand, especially from Fort Hamilton, which is five hundred yards in rear of the water battery, and the guns there mounted would need at least five degrees; their shot could have no ricochet whatever, and would generally sink where they strike the water.
Taking into consideration the deviation of the projectiles and the rapid movement of the steamers, the chances of oblique impact from the incurvation of the trajectory, the variety of curved surfaces forming a ship's side, and the constant change in their manner of presentation to the direction of the ball, it is probable that not more than one shot or shell in ten can be relied on at this distance to produce a maximum penetration.
The principal work on the left, Fort Tompkins, is situated on a high hill, and two other batteries (Hudson and Morton) are in elevated positions.* Their fire is therefore not so efficacious for short distances.
To an enemy which should thus attempt to escape the fire of Fort Lafayette, by steering in with the Staten Island shore, the guns of the water battery (Fort Richmond) would be very formidable.
This work mounts twenty-seven 42-pounders,* of which it is probable that not more than a third can be made to bear on any one point.
At two hundred yards, which is to be the nearest approach of the ships in passing, the maximum penetration of 42-pounder shot in oak will not exceed fifty inches.
T'he time of exposure to the fire of the fort would be about fifteen minutes for a sailing ship at the rate of eight knots, and about ten minutes for a steamer going eleven knots.
Would the damage received in that time be likely to injure so many vessels as to prevent the design on the city entirely, in consequence of the reduction of the force ?
In attempting to arrive at some satisfactory response to this query one is bound to avoid possible contingencies, and to adhere to those which experience has indicated as probable.
A shell properly placed will sink a ship; a hot shot will set her on fire; but it would be very unwise thence to infer that this would necessarily be the effect of every shot fired at the ship.
The Hornet sank the Peacock in fifteen minutes; but no naval officer would infer from the fact that a sloop-of-war could generally obtain a like result. So far froin that, it is unprecedented and may hardly occur again.
Uncertainty as to the distance, change of position, interposition of the smoke in a covered battery, lack of deliberation, will cause the failure of many shot to strike the object at all.
The exactly fatal spot is limited to a few inches of surface near the water line; in other places a ship will sustain a large number of shells.
The prodigious endurance of line-of-battle ships will appear to any one who will look over the records of sea fights. Hour after hour they have been known to sustain an unceasing fire at each other, with every gun on the whole broadside, and yet but one or two cases of sinking during a fight will be found.
See report of Board of Engineers.
Let us note a few instances of endurance that have occurred in well-known engagements :
In 1770 the Sandwich, ninety-eight, received seventy shot holes, seventeen of them between wind and water. (Rodney and DeGuichen.) She continued to form part of the English fleet, and cruised actively, as the flag-ship, until Rodney went home, eighteen months afterwards.
At Copenhagen, Nelson anchored his ships about three hundred yards from the Danish line, and received its fire for more than three hours. Of the fleet