THE INDUSTRY

stalks broken, about a foot from the lower end, by a man standing up to his knees inwater, who, holding a few of the stalks with the large ends from him, threshesthe water with them, till the broken pieces are separated and fall off. Thenturning them, he takes hold of the fibres that have been freed, and beats thesmall ends in the same manner, until the fibre is entirely separated from thestalks. A few strokes are sufficient. It is then dried and packed up for market.

The fibres imported from the East Indies under the name of Jute, appear tobe derived from the bark of two species of Corchorus, a plant allied to the Lindentree. It is cleaned and prepared by maceration in water and subsequent scrap-ing. It resembles the Sun hemp in many respects, but is somewhat finer, andpossesses less strength.

The well known gunny doth , of which vast quantities are yearly importedinto the United States, is not made exclusively from any one variety of fibre,the warp not unfrequently being of one material, and the filling of a totallydistinct fibre. Usually, however, it is composed of the fibres of the Crotalariajuncea (the Sun), and of the Corchorus (Jute). Flax and hemp neverenter into its composition. Gunny is imported into the United States in theform of cloth and bags; the quantity sent yearly from Calcutta, the prin-ciple shipping port for this article, is immense, amounting in 1849 to 114,239pieces, and 3,230,400 bags. Besides these importations, a large quantity is sentfrom the East Indies in the form of envelopes for other materials, as saltpetre,Java coffee, &c., &c. Owing to the great cheapness of the gunny, the bagsare rarely used more than once, before they fall into the hands of the papermakersand rag-merchants. In this condition they constitute the cheapest paper stockto be procured in the market; the demand for it is not, however extensive, evenat low prices, since it is impossible to bleach the fibres sufficiently to renderthem serviceable for the manufacture of white paper. This is owing to the fact,that the gunny fibre is procured from the bark of a tree, and contains a largequantity of humic and cremic acids, together with some mineral bases, and sometannin. These substances rapidly neutralize and destroy almost any bleachingagent which can be applied. The use of gunny is, therefore, wholy restricted tomanufacture of brown wrapping and envelope papers.

The most singular vegetable fibre of the East Indies, convertible into cordage,is the production of a Sago palm. This fibre is known best as Ejoa, and resemblesblack horse-hair. Each tree produces six leaves in the year, and each leaf yieldsten and a half ounces of the fibre, which makes the annual produce of the treeequal to about four pounds. Some of the best trees produce full one pound offibres in each leaf. They grow from the base of the foot-stalks of the leaves, andembrace completely the trunk of the tree. Both fibres and leaves are easily re-moved without injuring the tree. Gables made from this unique article are oc-casionally brought from India to the United States, but not as an article of com-merce. The cordage known in the East Indies as Coir, is produced from theshort, woody, and apparently intractable, husky fibres of the outer envelope ofthe cocoanut. These fibres are prepared by soaking the husks in water for a greatlength of time, not unfrequently exceeding six months, or until they become soft.The husks are then dried and beaten until the woody part falls out like saw-dust,leaving only the fibres. The cordage made from the fibres so prepared, is said tobe the finest that can be produced from any vegetable material.

The true hemp and flax are not grown in the East Indies to any extent for thefibres, but for the seed merely. Within a few years a society has been formed inLondon, under the auspices of the East India Company, to induce the natives topreserve and to prepare the fibres, as well as the seeds of these plants, but theirsuccess is yet quite indifferent. The natives are unwilling to give the labor andcare necessary to clean and prepare the delicate fibres of flax, especially since theyfind their wants fully supplied by the fibres of the Corchorus and Crotalaria , whichare cultivated and prepared with great ease and economy.

The fibre obtained in India from a species of nettle, and known as Chinagrass, Bhea fibre, and Calooee hemp, has recently attracted considerable attentionin Europe, especially in France. Treated with a hot solution of carbonate ofsoda, it assumes to a great degree the softness and lustre of silk, and in fact is nowused to a very considerable extent as the warp of certain descriptions of Frenchsilks. Specimens of this fibre, beautifully prepared, have been sent to the UnitedStates during the past summer, and have not failed to attract the attention ofmanufacturers. If the China grass should become an object of demand, unlimitedquantities can be obtained in India at an exceedingly low rate.

One curious fact noticed in regard to almost all fibres derived from endoge-nous plants, is that they do not admit of being tarred, and are not susceptibleto its influence as hemp and flax fibres are. This is particularly the casewith the Manilla and Sisal hemp. Tar in any case is applied merely to pre-serve cordage, not to strengthen it, and it is a well known fact, that tarred cordagewhen new is weaker than white fibres, and the difference increases by keeping.It is further worthy of notice that tar is not the produce of any trees growing inthe tropics, the natural habitat of the endogeneous plants yielding foliaceousfibres.

As a substitute for tarring cordage, the natives of the Indian Archipelago areaccustomed to tan their fibres, after they have been wrought into both twine

T4

OF ALL NATIONS.

and sail cloth. The treatment is said to give additional strength. The ap-plication of tannin to vegetable fibres has not been thoroughly investigated,and it is a question, whether as a preservative of cordage its operation might notprove highly beneficial.

ON MR. WHITWORTH’S MODE OF PRODUCING PLANE METALLIC

SURFACES.

M R. JOSEPH WHITWORTH is one of the English Royal Coii-iuissioners tothe American Exhibition; and all those who are interested in good toolsfor the construction of machinery, must have observed in their exploration inthe Crystal Palace, the lathes, screwing machinery, and other mechanical con-trivances of this very ingenious constructor. We propose to describe in thepresent article the method employed by Mr. Whitworth to produce plane metal-lic surfaces. All workers in metal are aware of the great difficulty of securingsuch surfaces with a degree of accuracy such as is required for nice work. It will beshown in the course of these remarks that the usual method of grinding withemery powder is incapable of producing a plane surface.

The surface plates exhibited by Messrs. Jos. Whitworth & Co., in the NewExhibition, are formed of cast-iron, and are remarkable for the high degree oftruth they possess, and for the mode adopted in preparing them.

If one of them be carefully slid on the other, to exclude the air, the two plateswill adhere together with considerable force, by the pressure of the atmosphere.The surfaces should be well rubbed previously, with a dry cloth, till they are per-fectly free from moisture, that the experiment may afford a fair test of accu-racy. If any moisture be present it will act like glue, and cause adhesion to takeplace, supposing the surfaces to be much inferior. But if they be perfectly dry,adhesion proves a high degree of truth, rarely attained.

The experiment may be varied, by letting one surface descend slowly on thoother, thus allowing a stratum of air to form between them. Before they comeinto contact, the upper plate will become buoyant, and will float on the air with-out support from the hand. This remarkable effect would seem to depend on thoclose approximation of the two surfaces at all points, without contact in any—acondition which could not be obtained, without extreme accuracy in both. Theescape of the remaining portion of air, is retarded by friction against the surfaces,the force of winch nearly balances the pressure of the upper plate. If one endof the upper plate be slightly raised and allowed to fall suddenly, the interveningair will act like a cushion, causing a muffled sound to be emitted, quite differentfrom that produced by the concussion of metallic bodies.

These surfaces, were brought to their present state by means of filing andscraping, without being afterwards ground. The method hitherto adopted ingetting up plane surfaces has been (after filing to the straight edge) to grindthem together, with emery. In some cases, it has been customary to try thempreviously on a surface plate, and to go over them with scraping tool; a but theyhave always been ground afterwards. The surface plate itself has been invariablytreated in the same manner. The process of grinding is, in fact, regarded as in-dispensable wherever truth is required. The present examples, however, showthat scraping is calculated to produce a higher degree of truth than has ever beenattained by grinding. In reference to both processes a great degree of misconcep-tion prevails, the effect of which is materially to retard the progress of improve-ment, and which is of great importance to remove. While grinding is universallyregarded as indispensable to a finished surface, it is, in fact, positively detrimental.On the other hand, the operation of scraping, hitherto so much neglected, con-stitutes the only certain means we possess for the attainment of accuracy. Afew remarks will clearly illustrate the truth of this statement.

It is required in a surface for mechanical purposes, that all the bearing pointsshould be in the same plane; that they should be at equal distances from oneanother, and that they should be sufficiently numerous for the particular applica-tion intended. Where surfaces remain fixed together, the bearing points may, withoutdisadvantage, be fewer in number, and consequently wider apart; but in thecase of sliding surfaces, the points should be numerous and close together.

A little consideration will make it evident that these conditions cannot be ob-tained by the process of grinding. And, first, with regard to general outline, how isthe original error to be got rid of? Let it be supposed that one of the surfacesis concave, and the other a true plane. The tendency of grinding, no doubt, willbe to reduce the error of the former, but the opposite error will, at the same time,be created in the true surface. The only case in which an original error couldbe extirpated, would be, when it was met by a corresponding error, of exactly thesame amount, in the opposed surface, and the one destroyed the other. But it isevident, that where only two surfaces are concerned, the variety of error in thegeneral outline, is not sufficient to afford any probability of mutual compensation.

It will further appear, that if the original error be inconsiderable, the surfacesmust lose instead of gaining truth. It results from the nature of the process, that