rejected theories, is respectively as half the versed sine, C, B, to half the arc, A, B, D, and by raising the chord, A, D, parallel with itself, towards B, we can press the contending theories to their ultimata, and see whither they lead us; for the rule will hold till the chord, in advancing, obliterate the arc. I trust that "E" will not "jump to the conclusion," that I undervalue the facility with which he expresses himself in algebraic notation; but to those who see this subject as I do, his solutions fail in effect-wanting, as we conceive, that essential element to correctness-the consideration of the flexibility of material. The preliminaries on which to found an equation are not agreed, and algebra cannot reason, or furnish ideas, although it afford a concise and convenient form of expressing them, be they correct, or

erroneous.

Cincinnati, November 10th, 1843.

American manufacture of Wire Ropes for inclined planes, standing rigging, mines, tillers, &c. By JOHN A. REBLING, C. E.

The art of manufacturing ropes of wire is comparatively new. Numerous attempts have been made in Europe and here, and most of them have proved failures. A collection of parallel wires, bound together by wrappings, in the manner of a suspension cable, is no rope, and not fit for running, it can only be used for a stationary purpose. The first rigging made in England, was of this description. The difficulty in the formation of wire rope, arises from the unyielding nature of the material; iron fibres cannot be twisted like hemp, cotton, or woolen; their texture would be injured by the attempt. To remove this obstacle, some manufacturers have resorted to annealing, and thereby destroyed the most valuable properties of iron wire, viz., its great strength and elasticity.*

My first attempts in the manufacture of wire rope, were made four years ago; my intimacy with the construction of wire cable bridges, induced me to investigate this matter. The principles of my process differ from those of the English manufacturers-they are original and secured by patent. The novelty of my proceeding chiefly consists in the spiral laying of the wires around a common axis without twisting the fibres; and secondly, in subjecting the individual wires while thus laying to a uniform and forcible tension under all circumstances. By this method, the greatest strength is obtained by the least amount of material, and, at the same time, a high degree of pliability. Each

By the term elasticity, I mean the property of wire to stretch and give when subjected to a strain, and to resume its former length after the strain ceases, without suffering a permanent elongation. The extent of elongation of iron is in proportion to the tension. In estimating the strength of a rope, the strain it has to support should never exceed the limit of elasticity. A permanent strain requires some more allowance.

The elongation of good wire of No. 14, 15, or 16, amounts, according to my own experi. ments, to 1-5000 of its length per ton per square inch. A strain of 15 tons upon a rope of 1 square inch section, and 1000 feet long, will produce an elongation of 3 feet. The limit of elasticity for working rope, I have assumed at 15 to 20 tons per square inch, according to the size and quality of the wire. A greater strain will produce permanent elongation, and if repeated, at last a rupture.

individual wire occupies exactly the same position throughout the length of a strand; another result of the precision and force applied in laying, is the close contact of the wires, which renders the admission of air and moisture impossible.

Three years ago I offered to the Board of Canal Commissioners, which was then in power in Pennsylvania, to put a wire rope of my manufacture on one of the planes of the Allegheny Portage Railroad, at my own risk and expense, the value of the rope to be paid in proportion as it rendered services equivalent to a hemp rope. This liberal offer, however, was rejected, and not considered until the present Board came into office. Last year I put three ropes, measuring, in the aggregate, 3400 feet, 44 inches circumference, in operation on plane No. 3. Owing to the want of adhesion, I had, at the start, to contend with some difficulties. By means of a double groove on the receiving sheave, and a guide sheave placed back of it, which crosses the rope, and leads it from one groove to another, which improvements were added to the machinery last winter; I succeeded in doubling the adhesion. When, in unfavorable weather, there is delay and slipping on the other planes, the wire rope can at all times pull as heavy a load without a balance, as the engine is capable of hauling. The planes of the Portage Railroad require hemp rope of S inches circumference, made of the best Russia, or Italian, hemp, and which cannot be trusted longer with safety than one season. They are frequently, from reasons of economy, continued 14 seasons; much, however, depends upon the weather and business. The unfavorable circumstances under which the wire rope had to work last year, affected it some; the wear of the whole of this season, however, is not perceptible, and its present condition promises a long duration. I am now manufacturing another wire rope of 5100 feet long, in four pieces, for plane No. 10.

The first rope of my make, 600 feet long, 34 inches circumference, has now been in successful operation two seasons, hauling section boats from the basin to the railroad at Johnstown. Two more were put to work last spring, at the new slips, at Hollidaysburg and Columbia. From my present experience, I may safely assert, that wire rope deserves the preference over hemp rope in all situations much exposed, and where great strength and durability is required.

By my process of manufacture, the same pliability is imparted to the rope which is proper to the wire itself. Paradoxical as this may appear, it is nevertheless a fact, and is easily explained. By pliability, is here understood the extent of flexure to which the rope, or wire, may be subjected, without producing a permanent bend; when released the rope must resume its former and straight position. To bend a rope requires force, and this force is in proportion to its areal section, cæteris paribus.

Well manufactured iron rope is more pliable than hemp rope of the same strength. I am manufacturing tillers of fine wire, capable of bearing 3000 lbs., and which ply around cylinders as small as four inches in diameter, and in which the wires are so compactly laid, that not the slightest shifting in their spiral position is to be observed.

number of my tillers are in use on the Ohio and Mississippi. Such rope would be pliable enough for running rigging, and be of long duration.

I will here add a few remarks on the introduction of standing wire rigging, in place of hemp rigging. This subject has, for some years past, engaged the attention of the Navy Department of England and France, and the success which has attended the use of wire in place of hemp for shrouds and stays in the naval and commercial service of Great Britain, would, it appears, seem to warrant an attempt to test its utility in our national vessels.

Allow me to cite here a few remarks from the notes of Capt. Basil Hall, on a tour through Switzerland, and while examining the wire suspension bridge at Freiburg. He says, "attempts are now making, and will ere long succeed, to introduce wire rigging, which is stronger and better than chain, because less dependent on the accidental quality and careless manufacture of a single part. How strange it is, that the plan of making wire bridges, so successfully adopted in France, and elsewhere, should not have found favor enough in England to be fairly tried on a large scale. Freiburg bridge, 301 feet wider than Menai, at least equally strong, has cost only one-fifth of the money. I do not think wire will answer for running rope; but for standing rigging it may, I conceive, be most usefully substituted for hemp, for, with equal strength, experience shows it to be lighter."

The cables of suspension bridges are stationary, and will, when protected against oxidation, last an indefinite period. Standing rigging, when compared to running rope, is nearly stationary, and there is little wear but what arises from the direct strain, which, if supported by sufficient strength, will have no deteriorating effect. In comparing the two materials, wire and hemp for rigging, the state of preservation, and time of use should be considered. For instance, a hemp stay of a certain size, made of the best Italian hemp, will, when new, possess two-thirds of the strength of a wire stay of the same weight per foot; but let the two stays have been exposed, and served five years, then the strength of the hemp stay will be gone, while the wire stay will not show any perceptible reduction. In this case, of course, a common wear and tear is supposed.

The most prominent features of wire rigging, as compared to hemp rigging, are its great durability, less weight and size, less surface exposed to wind, less danger in time of action of being destroyed by shot. Another good quality of the wire rope is its great elasticity, which is quite sufficient to counteract the effect of a sudden jerk while a vessel is rolling heavily at sea. The elasticity of hemp rigging is only to be relied on to a very small extent; it will give and stretch a great deal, but not return.

A common objection of those not familiar with the nature of wire rope, is its supposed rapid destruction by oxidation, but no apprehension is less founded than this. Running wire rope, while in use, either in or out of water, in mines, or any other situation, will not even require the protection of oil, varnish, or tar; while at work it will rust no more than a rail, or a chain, in use; but when idle, oxi

dation will affect it in proportion to the surface exposed. As, however, the process of laying is carried on with mathematical precision, by which the wires are brought into the closest contact, the assemblage of wires in form of a strand, present a solid rod, which will be no more subjected to rusting, than the link of a chain of the same size. The individual wires, as well as the strands and ropes, are coated with an excellent varnish during the manufacture. Wire rigging will require no other protection but oiling, or tarring, once or twice a season. Where elegance is an object, black or green paint may be used. Rigging made of zinced wires, and not painted, would present a most beautiful appearance, and be exempt from all rusting.

Wire rope can be spliced in the same manner as hemp rope. The attachment of wire shrouds to the sides of the vessel, and to the masthead, and their connexion with the rattlins, (which should also be of wire,) can be effected by the old method; the use of wire, however, will suggest some modifications better adapted to the material.

Some wire rigging has been manufactured in England, which simply consists of a collection of parallel wires bound together, and served over with hemp. These mixtures, as experience has proved in the case of tiller-ropes, are objectionable-the wire will rust inside of the hemp in spite of all protection by varnish; besides the cover of hemp, which adds nothing to the strength, is only an additional

expense.

Iron is now gradually superseding wood in the construction of vessels, a complete revolution in ship building has already commenced in England. Although very expensive at first, iron ships will prove cheapest in the end. Are there any well founded objections to wire rigging, which assumes the same relation to hemp rigging, as wooden ships to iron ones? There are none. Why then not test this matter by encouraging those who are capable of bringing it to perfection? A number of iron vessels are now building for the naval and revenue service, which seem to offer appropriate occasions for the test of this

matter.

Saxonburg, Pa., September, 1843.

The Forms of Ships.

Amer. Rail Road Journ.

The great importance of naval architecture induces us to return to the report of experiments conducted by a committee of the British Association for the Advancement of Science, which was read at their last meeting at Cork. The account copied into the last number of our Journal, from the Athenæum, was chiefly limited to the notice of the experiments themselves, and merely adverted casually to the deductions founded upon them, without describing the form of least resistance, which the committee recommend as the result of their five years' labors. We have since been supplied with a further account of Mr. Scott Russell's exposition, and, as the experiments have been more numerous, and have been conducted on a larger scale than any previously made on the subject, we think it desirable, in the absence

of the voluminous report of the committee and drawings, which may not be published for years, to state at least some of the results of these long-continued and costly experiments.

In Mr. Scott Russell's exposition of the labors of himself and Professor Robison, after mentioning minutely the mode in which they had conducted their experiments, and their results, he proceeded to describe the form of construction which they had determined to be the best, not only as offering the least resistance to motion through smooth water, but also as best adapted for rough seas. It is to be regretted, however, that in this, the most important part of his exposition, Mr. Russell was less explicit and not so minute as in describing the preliminary experiments. He stated facts, but did not explain the principles by which they were regulated, therefore it is difficult from one isolated form of construction, which was all he exhibited, to determine how far it is adapted to vessels of other sizes. He observed, that the great point which, in the first instance, was endeavored to be gained, was to get rid of the wave at the bow, which has the same effect in retarding a vessel as if it were immersed so much deeper in water. It was found that this object might be attained by lengthening the ship, and that whenever speed was required, there must be an absolute length without regard to breadth.

P

E

P

PT..

D

G

Mr. Russell having stated that each velocity has a corresponding form and dimension peculiar to that velocity, he exhibited the form of the light-water line of a steam vessel intended to be propelled with a velocity of 17 miles an hour, and explained the mode of constructing it. Suppose the breadth C D, of the vessel to be 25 feet, there must be set off forward from the greatest midship-section 120 feet, and for the after-part, 85 feet. To make room for the engines, there is no objection to putting in a piece in the middle of the vessel, called the middlebody, of equal width to the greatest midship section. On half the breadth of the vessel, fore and aft, describe the semicircles C, D, E, G. Divide the fore part, o A, into a given number of equal parts, and divide the semicircles also into the same number of parts; in the accompanying diagram, we have divided them into not more than four, for greater distinctness. Then draw lines parallel to the keel, A B, from the division o, o, o, of the semicircles to the corVOL. VII, 3RD SERIES. No. 1.-JANUARY, 1844.

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