THE NAUTILUS and her Hydraulic Propelling Power.

[In our number for May last we gave an account of an invention carried out in what was there termed "an hydraulic steamship." The application of hydraulic power to propelling vessels in place of paddle or screw, by the results of all the experiments yet made seems more than likely to displace all the present appliances of those powers; its advantages being steadiness as well as easiness of motion, and the cumbersome besides expensive nature of both those appliances outside of the vessel being entirely done away. Such enormous advantages, while a similar speed is maintained, seem to us to have been completely achieved, and must hereafter become general. We have received the following lines on the invention, to which we willingly give place; while the same process adopted in the Waterwitch is preparing for the Government.]

THE NAUTILUS.

A New Water Power.

The Nymphs and Naiads of the sea combined
To rectify the errors of mankind,

In those constructions that are seen afloat,
Propell'd by steam, and used in ship or boat.
For many years their nervous systems feel
The irksome pattering of the paddle-wheel;
They couldn't endure or tolerate the screw,
Which would their watery element slip through
More easily; and Morgan's feathering plan,
Or those, in graduated steps, which ran,
To them were merely mechanician's aids,
Hateful alike as common paddle blades!

Resolved such plague no longer to endure,—
This water bruising, and its noise to cure;
They hold a meeting and themselves install❜d,
Unto their council Dædalus they call'd:-
"Thou'rt an inventor, canst thou not produce
"(They say) some means adapted to man's use,
"By which his vessels may be made to glide
"Peacefully through the gentle, rippling tide;
"Without that thrashing of the aqueous
slave
"That breaks the stillness of the slumb'ring wave?
"Go, Dædalus, exert th' inventive power
"Thou canst command, submissive at the hour;
"And find for man some strong persuading force
"Which shall excel the power of the horse
"To boards applied; and your attention turn
"To water forces, whence he chance may learn
"Something to his advantage to pursue
"That's noiseless, easy, and efficient too;
"And will propel as well as boards or screw!”

To whom thus Daedalus replied:-"My best "And most untiring energies all rest

"At your command, most noble sisterhood!
"(Of rivers, lakes, and seas well understood);
"No longer shall those rude, old-fashion'd things
"Your peace disturb; and since old Time has wings
"To lend, we'll see if we can't have a look,
"And take a leaf from out of his old book!"

Off on his errand flew th' industrious man ;-
Consulted all the Argonautic clan,
On lore hydraulic, hydrostatic laws;
And with Archimedes discern'd the cause
Why water to its level rises, and the flaws
That oft prevent it; having cured them all,
A water power found with rapid fall:
With which his vessel gain'd the highest speed
That screw, or paddle, ever yet achieved;
All outside paddles, and the screw besides,
He does away, and flings this to the tides;
While those he uses, in hydraulic box,
Secure and easy under patent locks;
By means of them, a stream of water glides.
Swift through his craft, ejected at her sides!

Enough, by simple means his end he gains,
The vessel's speed rewards him for his pains:
His work approved, Dæd to the council hies,
And takes the Nymphs completely by surprise:
""Tis done," he said, "paddles shall not molest
"The quiet stillness of your lawful nest;
"No more shall those abominable waves
"Disturb the surface of your peaceful caves,

"Or send small boats unto untimely graves!"

་

While on his way the Nautilus he spies;

Pleased with her modest, graceful form he cries :-
"Since Nature's laws I have obey'd alone,
"The handsome Nautilus I'll make my own!

"For my invention her support I'll claim,

"For want of better, it shall have her name!"

Great was th' applause which through the council ran, As learned Dædalus explained his plan;

And soon those laws were pass'd which did provide That all the vessels which should henceforth glide On water surface of the Naiad's tide,

Should with the Nautilus power be supplied.

Those Nymphs no more of aching heads complain;
And thus a new propelling power we gain.

LIFEBOAT OARS.

We republish this thoroughly practical and interesting article on Oars from the Journal of the National Lifeboat Institution. We are sure that our readers will join us in an expression of great satisfaction with the committee of that valuable institution for instituting so successful an inquiry on a subject of so much importance.

As a lifeboat has, in the majority of cases, to be propelled by oars, and as, in order to rescue a shipwrecked crew, she has generally to be rowed to windward against a heavy sea and strong wind, it follows that too much care cannot be taken to place in the hands of her crew the most efficient instrument for the performance of their laborious as well as hazardous work.

Thus, in a description of the Shields lifeboat in the edition of Campbell's Lives of British Admirals, published in 1817, vol. viii., the following passage occurs:

"The oars she is equipped with are made of fir of the best quality, it having been found by experience that a rove ash oar which will dress clean and light, is too pliant among the breakers; and when made strong and heavy, from rowing double banked, the purchase being short, it sooner exhausts the rower; and this makes the fir oar, when made stiff, preferable."

In consequence, however, of the frequent breaking of the oars in the lifeboats of the National Lifeboat Institution, the attention of the committee of management has been recently directed anew to the subject, and by their direction a number of oars, made of different descriptions of wood, have been tested to ascertain their respective qualities.

Although to obtain very accurate results, it would have been necessary to destroy a much larger number of oars, yet the table appended, showing the result of the trials, so far, may not be without interest. It will be seen that three properties are designated as of value,-viz. lightness, stiffness, and strength; and if all three were of equal value, there would be no difficulty in arriving at a decisive conclusion as to the fittest description of wood for a lifeboat's oars, after testing a sufficient number of each sort. The question is not, however, quite so simple, and must after all remain a matter of opinion to some extent, as the above-named properties have different values, and even all practical rowers may not agree as to the relative value of each. We will remark on the three above-stated properties in succession.

1. Lightness.—It is of the utmost importance that a lifeboat's oar should be as light as possible, consistent with strength; for, however well balanced an oar may be, a greater effort must be required to move a heavy than a light one, and in proportion the sooner will a person become fatigued in rowing with the one than with the other; and, as

a lifeboat man will frequently have to make many hundred, and sometimes several thousand strokes with his oar before his object is attained, three or four pounds extra weight, like the last pound on the camel's back, may cause him to break down altogether. Since, therefore, an oar being heavy or light may make the difference of a rower retaining his strength of arm or not, and hence of reaching a wrecked vessel or not, too much attention cannot be paid to secure the greatest possible lightness, in conjunction, of course, with adequate strength.

As the only suitable woods for the making of oars are different species of fir and ash, and as all fir woods are lighter than ash, it follows that, in this respect, fir oars are to be preferred for lifeboat service.

2. Stiffness.-A stiff oar is considered to be more manageable in a rough sea than a pliant one, although in smooth water many men prefer rowing with pliant oars, especially those who have been accustomed to them. It is commonly supposed that there is a loss of power in rowing with a pliant oar, a certain portion of the force applied being expended in bending the oar. Such, however, is only to a slight extent the case, as no force once exerted can be absolutely lost, and the oar itself, in its effort to recover its normal condition of straightness before being withdrawn from the water, will continue the force first imparted to it after it has ceased to be made, in the same manner that a spring-board, in recovering its straight direction, enables a person to jump to a higher altitude or further distance than he otherwise could; the oar, in fact, merely acting as a medium for applying the force in an unequal and more prolonged manner. A slight degree of pliancy in an oar is probably, therefore, not a disadvantage, although much pliancy would be.

3. Strength. It will no doubt be supposed by most persons that an oar cannot be too strong, and that therefore great strength is the most important element in a lifeboat's oar. Up to a certain amount of strength, such is the case, and every oar in a lifeboat should be so strong that the most powerful man could not break it in rowing; but beyond that amount, independently of unnecessary strength involving greater weight, it becomes a question whether additional strength may not be a positive and possibly a serious disadvantage, even to the extent of endangering the safety of a boat.

The most frequent cause of the breaking of oars in a lifeboat is her being struck by a broadside surface, when the lee gunwale being forced under water, the men on that side cannot raise the blades of their oars sufficiently high to prevent their becoming immersed in that case the pressure of the water on the blades, as the boat is being carried, broadside on, at the rate of several miles an hour before the sea, is so great that the oars are forced from the rowers' hands, and retained in a nearly upright position, with the blades several feet below the bottom of the boat. If the boat be in shallow water, they then come in contact with the ground and are instantly broken, whilst, if in deeper water, they generally are so; and if from their great strength they were not to

break, the strain on them is then often so great that they would wrench the thowl-pins out of their sockets, and break the gunwale of the boat; or, if the latter were too strong to give way, the risk of the boat upsetting would be much increased, as the pressure of the still water on the blades of the oars beneath the boat, and that of the crest of the sea on her upper side in the opposite direction, would powerfully tend to that effect.

In selecting the most suitable description of oar for a lifeboat, we have then to decide on a maximum of desirable strength, and on a limited flexibility or pliancy, and to select the lightest description of wood that possesses those properties.

An analysis of the table below shows that by far the strongest oars are those made of ash, but that they are also the heaviest; whilst if reduced in size to an equal weight with a fir oar, they would then be much more pliant, owing to the greater flexibility of ash wood.

Thus the lightest ash oar tested, of those made of uniform size, was 19 lbs., whilst a weight of 22 cwt. suspended at 1 foot from the end of the blade, equivalent to three times that amount or 84 cwt. of force, applied at the handle, caused no less than 5 feet of deflection without breaking the oar.

But the lightest fir oak, a Norway spar, of only 143 lbs., broke on the suspended weight amounting to 1 cwt. 3 qrs. 23 lbs., equivalent to a force of 5 cwt. 3 qrs. 13 lbs. at the handle, whilst its deflection at 1 cwt. on the blade, equal to 4 cwt. at the handle, was 1 foot 10 inches.

Now there can be no hesitation in pronouncing the latter of these oars to be preferable to the former. No rower could have broken it by his own strength, without exerting a force equal to more than 4 cwt., which is much more than he could do: its pliancy was not great, and with every motion of his arms, he would have had to move 34 lbs. less actual weight than with the lightest ash oar.

On the other hand, if, as for the reasons above stated we believe to be the case, there is a limit to desirable strength, the greater strength of this, the lightest ash oar would have been an actual disadvantage.

It might, however, have been reduced in size and weight, but its pliancy would thereby have been much increased.

It will be observed, by Table III., showing the average quantities, that twelve descriptions of oars were tested, two of them being of ash, American (United States) and Quebec, and that ten descriptions were of fir of various sorts. If from the latter we reject American pitch pine and larch, on account of their weight and too great pliancy, Baltic yellow batten for its pliancy, Quebec yellow batten for its weight, and Quebec white spar for its deficient strength, we have remaining, from which to select, Norway and Baltic white spars and battens, and the peculiar wood the Oregon or Vancouver's Island pine. This latter wood has not hitherto been used for oars, but has been solely, we believe, imported for the masts of yachts, for which