Part 12
Fortunately, in the creation of a steam-fleet, the United States will not have to encounter tedious and costly experiments, nor to incur the risk of failure.[1] The best form of hull, model of propeller, and plan of engine are already so well established, that it is not easy to fall into error; that which is most to be guarded against is the popular demand, the prevailing mania for high speed,--for which single advantage there is such a proneness to sacrifice every other warlike quality. That measure of speed or power which will enable a ship to stem the currents of rivers, to enter or leave a port in the face of a moderate gale, or to meet the dangers of a lee-shore, should, it is conceived by many, be sufficient; and for these exigencies a ship, which, with four months supplies on board, can in calm weather and smooth water make nine to ten knots under steam, has ample power. This moderate rate is far below the popular mark; but, in considering this important question, it should not be forgotten, that, unlike the paddle, the screw will always coöperate with sail,--and that, if a ship would go far under steam, she must be content to go gently. The natural law regulating the speed of a ship is, that the power requisite to propel her varies as the cube of the velocity.
[Footnote 1: The constructors and engineers of the navy are unsurpassed in professional art or science, and when conjoined with naval officers--who should always determine the war-like essentials of ships--they are capable of producing a steam-fleet that would meet the requirements of all reasonable conditions. We venture to say, that the failures with which they have been charged would be found, on investigation, to be solely attributable to undue extraneous influences.]
Let it be distinctly understood what power is here meant. As the power applied to the propulsion of a vessel is only that which acts upon her in the direction of the keel,--and as, of the gross indicated power developed by her engine, one portion is absorbed in working the organs of its mechanism, another in overcoming the friction of the load, while still other proportions are expended in the slip of the propeller and in the friction of its surfaces on the water,--only that portion of the gross power which remains is applied to propulsion; and it is this remainder which varies in the ratio of the cube of the speed.
Hence a steamer, that with five hundred horse-power can make eight knots per hour, will require rather more than one thousand horse-power to drive her at the speed of ten knots,--the law being thus modified by the increased resistance consequent upon the greater weight of the large engines; and thus a limit to speed is imposed, depending upon the weight of machinery which, relative to her dimensions, a ship can carry. A ship, that at the rate of ten knots under steam may run twelve hundred miles, can, at the speed of eight knots, and with the expenditure of rather less fuel, run the distance of eighteen hundred miles; and therefore it is, many contend, that a man-of-war for distant service should not be laden with large engines, whose full power can rarely be wanted, and which monopolize so great a space and displacement as to render it impossible to carry fuel for their proper development.
It is true, that, with large power of engine, the vessel may command, so long as her coals last, the advantage of high speed, and her large cylinders will enable her, by working the steam very expansively, to use her fuel with great economy; but there still remains the disadvantage of the increased first cost of the machinery, and its greater weight and bulk, to be permanently carried, whether used or not, and which, by increasing the displacement of the vessel, proportionally diminishes her speed.
The last great improvement in connection with the screw remains to be noticed, namely, lining the "bushings" and "bearings" with lignum-vitae,--the invention of Mr. Penn, of Greenwich, near London.
The lignum-vitae is introduced in the manner shown in the drawing. In connection therewith, it must be said, that the length and diameter of bearings has been increased far beyond the proportions of former years. The "brasses" are bored out about three-sixteenths of an inch larger than the shaft; then the recesses are slotted out for the reception of the wooden strips. If care be taken with this part of the operation, any number of strips can be supplied ready fitted, and to put in a set of spare strips becomes a short and simple operation.
[Illustration]
Strange as it appears, these wooden bearings are far more durable than those of metal, and in some ships they have endured for years without any perceptible wear in those parts which, previously to this invention, had occasioned so much trouble and expense. But for this important discovery, it is thought by some of the most competent engineers that they would have been compelled to abandon the use of the screw in heavy ships.
The Napoléon, the type of the new steam-ships of the line in the French navy, is a good illustration of a first-class, full-powered steamer.
Her dimensions are as follows:--
FT. IN. Length extreme. 262 6.40 Length at load-line. 234 0.94 Beam. 53 8.38 Height between decks. 6 8.72 Height of lower port sill. 7 2.63 Depth of hold. 26 9.34 Deep-load draft. 25 3 Immersed cross section, sq. ft. 1063.48 Displacement. tons. 6050 Diameter of cylinders. 8 2.45 Length of stroke. 5 3.06 Diameter of propeller. (4 bladed) 19 0.70 Pitch " " mean) 37 11
She has eight boilers, each having five furnaces, consuming, at full speed, (12.14 knots,) 143 tons of coal per day, for which she stows five days' supply. The boilers and engines occupy eighty-two feet in the length of the ship.
The trial of this ship has established the practicability of adapting a propeller to a ship of the largest class, so as to insure great speed, and constitute a most effective man-of-war for certain purposes and in certain situations; but when the great weight of the engines is considered, and the large space they occupy in the vessel,--thereby diminishing the stowage of supplies,--and further, that, after the coal is exhausted, the ninety-gun ship has but the sail of a sixty-gun ship to rely upon, it is not easy to avoid the conclusion, that, however useful such a vessel may be for short passages,[1] and in those seas in which her supplies of coal and provisions may be constantly replenished, her sphere of action must be very limited, and she could not be relied upon for the long cruises and various services on which an ordinary line-of-battle ship is employed.
[Footnote 1: For debarking a regiment or two of Zouaves on the shores of the Adriatic or upon the coast of Ireland.]
A ship constructed on the plan of the Napoléon, for the sake of gaining a speed of twelve knots per hour for the distance of about two thousand two hundred miles, is compelled to sacrifice a great part of her efficiency in several most important particulars.
In time of war, at short distances from port, for the defence of bays or harbors or the Florida channel, for the speedy transport of troops to an adjacent coast, or to force a blockade, such a vessel would undoubtedly be a most valuable addition to our navy: but her employment must necessarily be confined to such circumstances and such situations; for should she unluckily fall in with an enemy's squadron, with her coal expended, or her machinery rendered useless by any of the numerous accidents to which steam-machinery is so constantly exposed, with her comparatively light rig, and want of stability in consequence of losing so great a weight of coals, she would hardly prove a very formidable opponent.
Therefore, while admitting the importance and necessity of providing for special service a small class of fast, full-power steamers, it is submitted that the auxiliary screw-steamer is the description of ship to which the largest and best consideration should be devoted; for to the nation possessing the most efficient fleet of such vessels must belong the dominion of the sea. And while their cost is counted, let it at the same time be remembered that their value can be estimated only by the character of the service they may render, and that their capacity for aggression abroad makes them the best defence at home.
Having briefly referred to the various views entertained in regard to the steam-power with which the navy should be furnished, it will be seen that a difference of opinion on this important subject may most reasonably be entertained.
None can doubt the advantages of celerity to a man-of-war, yet many believe it would be too dearly purchased by the sacrifice of space to such an extent as would require supplies to be often replenished; as this necessity would in war confine the operations of the navy to our own shores.
On the other hand, it is admitted, that, without high speed, a ship of war cannot exercise many of her most important functions,--that she can neither choose an engagement, protect a convoy, nor enforce a blockade.
The best experience affirms the policy of giving to our cruisers as large steampower as is consistent with a due development of all other warlike qualities; for what would avail the superior armament of a ship, if the option of fighting or flying remain with her adversary, which must be the case when the latter commands higher speed? The introduction of improved ordnance, throwing heavy shells with great precision at long ranges, gives increased importance to celerity; for in any future fleet-fight, victory should belong to that flag having at command a steam-squadron of superior speed, which may thereby be concentrated upon any point without having been long under fire.
May not the command of a maximum speed of thirteen knots be obtained from the machinery now employed for a maximum speed of ten knots? It evidently may, and with great economy, too, by the simple introduction of artificial draft, and the use of steam of higher pressure, when requiring the highest speed. At present, in our men-of-war, the boilers are proportioned for natural draft, burning about twelve pounds of coal per square foot of grate per hour, and for a steam-pressure of fifteen pounds per square inch. If, then, the boilers be proportioned to burn at the maximum, with blowers, say twenty-two pounds of coal to the square foot of grate, and to generate steam of forty pounds to the square inch, we shall double the power developed by the machinery, and consequently derive from it the same speed that could be attained without blowers from double the machinery; while the natural draft and the usual pressure of fifteen pounds would give sufficient speed for ordinary service. The inconvenience of the higher pressure with blowers could well be endured for the short and occasional periods during which they would be required.
To create a perfect screw-frigate, a ship with sail-power complete, and efficient for any service that may be required, the endeavor should be made--by getting rid of every dispensable article of weight or bulk, and without reducing supplies below three months' provisions and six weeks' water--to find space and displacement for an engine of sufficient force to drive her thirteen knots an hour, together with at least ten days' full consumption of fuel; and this, it is believed, might be successfully accomplished in ships of the dimensions of the Wabash, beginning with a judicious reduction of spare spars, spare sails, and spare gear, and by the addition of blowers to their present machinery: a subject which should immediately receive the earnest consideration of a commission of the most intelligent officers.
Having fixed upon the proportions of hull and spars, the form of propeller, and the plan of engine, a cautious discrimination should be exercised in multiplying the types of either. Besides economy, many other advantages would flow from a judicious regard to similarity in build; as it would permit us to relieve our ships of many of the spare spars with which they are incumbered, and we should probably not again hear of suspending the operations of a frigate thousands of miles away, until a crank or rod could be sent to her; because, when ships of the same class are cruising together, by a careful distribution of spare spars and machinery among them, it is hardly probable that damage would be sustained, or loss of spars or "break down" occur, which might not be remedied by the resources of the squadron.
On the other hand, this system not be carried to a Chinese extreme, lest we follow too long a false direction,--thus losing the advantage of improvements constantly being made. For such is the change in all things pertaining to maritime war, that neither model of hull, plan of engine, nor mould of ordnance is best, unless of the latest creation. True progress will be most judiciously sought in not departing too suddenly and widely from the established order.
WHITE MICE.
A great many circumstances led me to decide on leaving the convenient boarding-house of Mrs. Silvernail: a house correctly described as containing several "modern improvements": improperly, as being "in the immediate vicinity of all the places of public amusement." For, as the Central Park of New York is a place of public amusement, so likewise is Barnum's Museum; and these two places being at a distance of about five miles from each other, how could any one house be in the immediate vicinity of both? But it was not upon this incompatibility that any of my objections were founded.
If I have a prejudice, it is against being talked _at_ instead of _to_. Now Mrs. Silvernail, who, like the katydid of the poplar-tree, if small, was shrill, had a way of conveying instructions to her boarders by means of parables ostensibly directed at Catharine, the tall Irish serving-maid, but in reality meant for the ear of the obnoxious boarder who had lately transgressed some important statute of the house, made and provided to meet a case or cases.
A landing-place on the stairs was usually the platform selected for the delivery of a monologue, in which Catharine was always assumed to be the person addressed; although I have known instances in which that "excellent wench" was, at the time of being so conferred with, in the grocery at the corner, about half a block distant, as I could see from the window where I sat and viewed her protracting her doorway dalliance with Jeremiah Tomaters, the grocer's efficient young man.
"Catharine," my landlady would say in a loudish whisper, close by a malefactor's chamber-door, and probably when Catharine was yet far down the street,--"Catharine, who let the water in the bathroom run over just now? If the slippers he left behind him a'n't Mr. Jennings's, I declare! Boarders must be warned an' watched, elseways we shall hev all in the house afloat, 'cepting the stoves an' flat-irons, by-'n'-by. Somebody at Mrs. Moyler's acted so, and the house was like a roarin' sea, with the baby adrift in his little cradle, and the roaches a-swimmin' round. Oh, dear!"
Now Mr. Jennings was the serious boarder, who lodged in the room just over mine: a man who, from general indications, had never had a bath in his life; certainly he had never troubled the waters in that house. I was the supposed delinquent, and at me the parable was levelled.
"Catharine, whose pass-key was that you found in the door? It's a mussy we wasn't all a-murdered and a-plundered in cold blood, by the light o' the moon! Mr. Jennings's night-key it must have been, to be sure! Boarders must be warned and watched. When Mrs. Toyler's nephew's night-key was found in the door of Number Forty-Seven, the boarders all went off at daylight in an omnibus, takin' away custom and character from the house forever."
Now Mr. Jennings, the serious boarder, was always in bed and asleep long before latch-key time came round; and even supposing he ever _had_ let himself in by means of that mischievous little convenience, he would as soon have thought of taking the door up to bed with him as of leaving the key in it. The parable was intended for the hearing of a young man who occupied the room opposite mine, and who, being connected with clubs, came home nobody ever knew when or in what condition, but had red eyes o' mornings and a general odor of the convivial kind.
Then, again, Mrs. Silvernail had a way of being always about the doors of the rooms, and a faculty, as I thought, of hovering near several of them at one and the same moment. There are men who will turn the least promising circumstance to advantage,--even that of being listened at through a keyhole, while they discourse to themselves about affairs connected with their most cherished and secret designs. One Captain Dunnitt, who lived in the house before I came, adroitly made his account of this eavesdropping propensity of the landlady, by settling his weekly bill with a silver-mounted pistol, instead of the dollars justly due. He had been a tragedian as well as a captain, and was saturated with Shakspeare and other bards to a far greater amount than with money; and when his week came round, he used to stride up and down his room with much gnashing of teeth and other stage indications of distress, finally settling down into a chair before the table, on which he would place and replace a packet of letters and a wisp of unromantic-looking hair. Then he would take the little silver pistol from his breast, and, after the usual soliloquy of "To be or not to be," or something equally to the purpose, would point it at his temples just as the landlady came bursting into the room, begging him for all sakes not to "ruin the character of her second-best room, and the walls newly painted at that!" Remorse would then double up the manly form of Captain Dunnitt, who would fall on his knees before the landlady,--"his benefactress! his better angel!"--and then arrangements would be entered into by which he was not to commit suicide for the present, but could avail himself of the landlady's indulgence and wait for "that remittance," which was always coming, but which never came.
But there were more serious objections, even than a landlady of shrill parables and an inquiring turn of mind, to my prolonging the delights of a residence at the first-class boarding-house of Mrs. Silvernail. Not the least of these was the fact of its _being_ a boarding-house,--a community. In such communities, from the inevitable intercourse over the social board, your circle of acquaintance is always liable to be extended rather than improved. In them there is no escape from the disinterested offers of those who would be your perpetual friends. I am still under lasting obligations to a man who, at a boarding-house in which I sojourned for but three days, forced on me a pipeful of an extremely choice and luxurious kind of tobacco, to dilate on the properties of which he came and smoked about a quarter of a pound of it in my room that very evening, and far on into the morning light. His goodness is the more impressed upon my memory, because, on the same occasion, he drank the greater part of the contents of a large willow-bound bottle of old St. Croix rum, which I had just received from a friend who had imported it direct. Then, in boarding-house communities, one's magnetism is as much at fault as that of a ship sailing up a river whose rock-bound shores are impregnated with iron elements. I knew a man who was over-magnetized to the extent of matrimony by the lady of the house,--a widow, and a shrew. He hated, or at least professed to hate her, and had ridiculous stories about her to no end; but she married him, and he still lives. Another, of a rather unsociable turn, rejected the proffered civilities of all his fellow-boarders who ever came to offer him rations of curious tobacco or to assist him in performing a libation of old and valuable Hollands. The only one of the party to whom he ever "cottoned" was the latest comer, a smoothed-out, blandulose kind of man, who smoked up all his cunning cigars, made sad havoc among his Hollanders of gin, departed from that house in an unexpected manner and his friend's best trousers, in the pockets of which he had bestowed that friend's rarest gems and gold, and is now serving out a term allotted to him in the State Prison, in recognition of the remarkable abilities displayed by him in the character of what the police call a "confidence man."
And yet there are more objectionable boarding-house acquaintances than people who insist upon sharing with you their friendship, be they "confidence men" or not. I suppose we may allow, in these advanced times, that it is something like magnetism which decides the question of affinity and its reverse. But, in granting this, I will take the liberty of observing that external and palpable facts have a considerable effect in directing the currents of magnetism. For example, and to adopt the language of scientific men, the insignificant circumstance of a person habituating himself to the partial deglutition of his knife, while partaking of food, may produce antipathetic emotions on the part of others, whom prejudice or superstition has led to regard the knife as an article designed for cutting only. This kind of outrage I allude to merely for the purpose of illustrating a case. In first-class boarding-houses, like that of Mrs. Silvernail, such rusticities have long since become traditional, and of the things that have passed away; and, indeed, so particular was that lady with regard to her knives, that, had a boarder swallowed even a part of one, he would undoubtedly have heard the deed alluded to through the keyhole of his chamber-door on the following day, in the form of a parable having for its hero the justified Mr. Jennings, our serious young man.
If external and palpable circumstances, then, are admitted to have a decided effect upon streams of magnetism, I suppose we may assume that they have also a certain power of determining impressions by themselves, without the intervention of any of the more subtile agencies whatever. The granting of this postulate will put me on quite easy terms with regard to the very positive objection entertained by me towards a certain Mr. Désolé Arcubus, who, by provision of an immutable Medo-Persic edict promulgated by Mrs. Silvernail, occupied the chair next mine at the first-rate table of that rigid expounder of boarding-house law.