CAPTAIN CARPENTER'S VESSEL

PROPELLERS.

A vessel-propeller, the same, except in point of position, with that which is the subject of the present article, was brought before the public about a twelvemonth ago, having been patented by a Mr. J. J. O. Taylor. The extravagant statements put forth as to the powers of Mr. T.'s invention in comparison with the common and other paddle-wheels, prevented many from giving it much consideration a glance being sufficient to convince any one at all acquainted with the subject, of the impossibility of its performing a tithe of the duty for which credit was claimed.

Capt. Carpenter, of the Royal Navy, subsequently improved upon Mr. Taylor's plan. Instead of one propeller under the dead wood of the vessel, Capt. Carpenter employs two, one on each side, near the stern. In this form, and as an auxiliary power to that of the wind and sails for sailing vessels, it is well deserving of attention, and, in that character, we now lay it before our readers.

From a prospectus issued by Captain Carpenter, we extract the following statement of the advantages which he believes to be possessed by the plan.

"It has been the opinion of many distinguished naval officers, captains of merchant ships, pilots, and scientific engineers, that the principle upon which I propose to propel vessels, as exhibited on a model, would be of infinite service to navigation, if a similar effect could be produced on a large scale; I have, therefore, considered it my duty, as the subject lies within the precincts of my profession, to demonstrate that principle, so that it may not be lost to mankind.

"The Euclid, an experimental vessel, 69 feet in length, has been fitted with this apparatus, from which it can be clearly proved that the propellers would be essentially useful to vessels under the following circumstances:

"1. To vessels that are tacking or veering in a narrow channel, amongst dangerous rocks and shoals, with light variable winds, and a strong current, and require to perform their evolutions with the greatest certainty.

"2. To vessels that are becalmed near the entrance of a port, and are desirous of coming to a safe anchorage before dark, and only require to be propelled a short distance to accomplish their object.

"3. To keep vessels clear of their anchor.

"4. To assist vessels in casting or winding, and backing astern.

"5. To enable a vessel to be steered independent of the rudder, should it be disabled.

"6. To assist vessels out of a dangerous position, should an accident occur to their masts or sails.

"7. To Indiamen, transports, emigration ships, or other vessels that have many persons on board, this novel apparatus will afford the crew an opportunity of being usefully employed in propelling the vessel a-head during calms, and prevent that monotony, delay, and expense, which ever accompany distant voyages.

"8. To vessels that are trading on coasts infested with pirates, and require, in a calm, to direct their broadside towards the enemy, to keep them off.

"9. To vessels that are trading up rivers, such as the Gambia, where manual labour is cheap, and tedious calms are prevalent, when the use of the propellers would shorten the passage (probably many weeks), and be of great advantage to the owners.

10. To ships of war, in taking up an advantageous position in action, particularly if opposed to steam frigates in a calm, or concentrating their fire in breaching a fortification.

"11. To ships of war, fitted both for sailing or steaming as may be deemed necessary, especially those that are stationed in a blockading squadron, and are required to intercept the enemy, if they attempt to escape in a calm, or in the event of the wind being favourable, possessing the means of topping up the propeller immediately out of the water, and making sail to economise their fuel.

"12. To yachts that desire the means both of sailing and steaming.

13. To iron boats fitted for transporting troops across rivers or lakes, worked by manual labour, keeping the men safe under cover from the enemics fire, till they are ready to disembark.

14. To canal-boats for navigating in shallow water, and amongst weeds, where the propelling blades require to be readily cleared, and their action in the water directed so as not to injure the embankments.

"15. To steam-vessels generally, that desire to do away with paddle-wheels, and to supply their place by a more safe and effective apparatus, that will give the same speed, and not incumber the vessel or alter the present mode of construction, that will remove the weight and inconvenience of the paddlebox, afford more room on deck, and allow boats to come alongside with safety.

"The novelty of the invention consists in the position which has been selected for applying this peculiar propeller, and the manner

in which it is affixed to a vessel so as to render it practically useful."

In thirteen out of these fifteen "circumstances," we think that Capt. Carpenter's propellers would be useful auxiliaries. To the fourteenth and fifteenth, it appears to us they could never be advantageously applied. In canals (to mention one objection on this head) where the water is generally shallowest, viz., towards the sloping banks, it ought, to allow of this propeller being properly effective, to be the deepest. As to its application to steam-vessels generally, as a substitute for the paddle-wheel, we need only point out that the power is communicated to the propeller by a universal joint, and that the propeller acts at a considerable distance from any solid bearing, to convince marine engineers of the inapplicability of the plan.

A model of a steam-boat, fitted with

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this apparatus, has lately been exhibited working on the canal of the Polytechnic Institution. On this toy-like scale the plan works beautifully, but the idea of forming a judgment from such an exemplification is out of the question. A vessel suitable for canal navigation, we are informed has also been constructed, called the Aerolite, of the following dimensions, viz: length of keel, 65 feet; draught of water with engine on board, 2 ft. 2 in.; extreme breadth, 8 ft. 11 in. The prospectus states, that "the efficacy of this principle of propelling has been well tested by manual labour, in this vessel, on the Thames, and on the City canal. We have not, however, been favoured with any statement of the experimental working of this "test," which would have given better data for observation than the action of the Polytechnic Institution model.

many practical and scientific improvements, particularly in the construction of hygrometrical instruments.

C 2

The desiccation of many crystallized salts, for example, sulphate of soda, in a dry atmosphere, happens both at high and low temperatures, and, in either case, the transparent solid crystals, become a dry opaque powder. A remarkable instance of this kind also occurs if cream be frozen into thin sheets and exposed to a dry cold atmosphere, about zero, when the whole of the water of crystallization vanishes, and leaves a fine powder of dry curd and butter. This process is adopted in the higher Swiss Alps, where perhaps churning is found to be impracticable, by placing sheets of iced cream perpendicularly in a frame, like a plate rack, between two open windows, the desiccated cream falling down into a receiving dish, and forming a delicate substitute for butter.

I have often noticed the rapid disappearance of snow during a dry black frost, and this seems to depend on atmospheric absorption, for it occurs during the night more than in day light. A fallowed field shall be wholly covered with snow so as to conceal the colour of the earth, and in one night of intense frost it disappears before the morning, without any intervening thaw. I am, Sir,

Your obliged reader,
ANTHONY CARLISLE.

Langhorn-place, London.

IMPROVED MECHANICAL AGITATOR.

Sir,-Much diversity of opinion exists in the political world, as to the utility-as well as the best method of conducting"agitation." I trust, however, that few persons will venture to question, much less deny, the value and importance of agitation in the perfecting of many useful arts and manufactures; but for some most ingenious applications of this principle, I fancy I should hardly have obtained the paper whereon to write this communication, nor the little steel instrument with which it is penned. Now without the slightest wish to interfere with, or to rival Dan. O'Connell, Esq., M.P., the most celebrated agitator of the dayyet, have I, like him, been endeavouring to introduce" an improved system of agitation.'

The accompanying camera-lucida sketch, represents a "mechanical agitator," or "shaking machine," which I de

signed between two and three months since, for a steel pen manufacturer. The action of the machine has been much admired, and it has been applied to some other useful purposes, besides that for which it was originally intended. In the manufacture of steel pens, there is always a slight bur raised on the edges of the metal, by the cutting-out process; in the subsequent operations of annealing, hardening, tempering, &c., the surface becomes scaly and discoloured, all which defects are very conveniently removed by shaking the pens together in large quantities; the effect being assisted by the presence of some abraiding substances, as sand, ashes, sawdust, &c.

The old method of accomplishing this object was, by placing the pens and the polishing materials in a bag, and shaking them for an hour or two; this, though a tolerably efficient, was nevertheless a very tedious operation, and it was soon superseded by a metallic cylinder or barrel, mounted upon two horizontal guides, which it was made to traverse backward and forward by means of a crank. In this machine, however, the motion of the pens was too rapid, and they struck against the alternate ends of the cylinder with great violence. An improvement upon this rude apparatus consisted in supporting the cylinder itself upon two cranks, which caused it to take an oval path, by which means the pens were turned over and over at each revolution. The extreme difficulty, however, of getting two cranks so accurately made as to work smoothly and evenly together, induced me to adopt the following method of obtaining the beneficial results in a more simple man

ner.

same

mend Mr. Pritchard to try the Mina Nova, a stone next in hardness, I believe, to the diamond, and obtainable in the Brazils for comparatively nothing. Some years since, I brought a quantity of them to England to be cut, and the first lapidary in London informed me, that only his diamond lathe would touch them. At that period he did not know what they were, nor did I tell him; but since then they have been imported from time to time, and are now readily procurable in this country. They are very brilliant when polished and the rays are perfectly colourless, which may be an advantage when so applied. At all events, if they should not be found equal to the diamond for microscopical purposes, they will be likely, from the regularity of their crystallization, to be much superior to glass.

W. A. KENTISH.

SAND FOR THE MANUFACTURE OF

GLASS.

Sir,-In one of your numbers I observed an account of some experiments made from sand, brought from New Holland, and used here in the manufacture of glass. A few bags of this silicious material were, on one occasion, imported at Liverpool, and bought up eagerly by the glass manufacturers, in consequence of its superiority over all other descriptions hitherto known in this country. I saw a specimen of it at the time, which certainly appeared to be very pure. A much finer kind, is however, in my opinion, obtainable with great facility and much nearer home. When in sight of the Brazils, between the latitudes 9° and 13° south, a passenger, on catching the first glimpse of the coast, invariably exclaims, "what an immense quantity of white linen is extended all along the shore!" or something to this effect. When he is assured that it is sand which has deceived him into this impression, he is credulous, until the nearer approach of the vessel confirms the fact. Now, as many hundred cargoes of cotton are forwarded from the Brazils yearly to England, this sand might be brought as ballast at a very trifling cost and sold here to considerable advantage. Parties interested in ship

ping have only to give instructions to their houses there to procure and place it in depôt, ready to be taken on board instead of large stones, which are frequently had recourse to for the purpose. These cost a good deal to ship on that side, and no little to unship on this, and are then unprofitable. Whereas, the sand would be likely to pay a good freight home, and may possibly, in addition, leave a larger profit to the shipper than any other article on board. Yours respectfully,

W. A. KENTISH.

A TREATISE ON THE BOX OF MATHEMATICAL INSTRUMENTS.*

This, as an elementary work will be found an invaluable acquisition to the young student at school, as well as to the mechanic and engineer. It contains a minute explanation of the nature, use and construction of the various lines marked on the protractor, plum scale, sector and slide-rule, adapting them to an extensive course of linear, superficial, solid, and angular mensuration. cluding practical geometry, surveying, measuring of timber, cask and malt gauging, heights and distances, falling bodies, vibration or pendulums, weights of persons, cattle, water, minerals, metals, balls, shells, &c.

In

The

In the preface the author very justly observes, "The instruments whose uses it explains, are often so little understood, that nearly half of them are of any service to their possessors. The sector, the most important in the box is generally regarded as unintelligible. slide-rule is briefly noticed in some treatises on mensuration, but as the pupil is presented with only a few formal precepts how to use it, without knowing why, he never understands its nature, nor the method of determining the value of any result, and he therefore lays it by with disgust.

"In the present work, every thing relating to the numbers is explained, their nature, construction and the mode of ascertaining their values, the method of obtaining the gauge points is also shown.

By Mr. T. Kentish, published by Relfe and Fletcher, 17 Cornhill.