The old, and now almost entirely. supeneded,ina think* termed a. mangle, gives, the moat simple and ' rude approximation towards miender ing,.and tire substitution of armies few plane sur faces. Its operation is. that u. a cylinder applied to a on which it is rolled backward and forward, moil some degree of smoothness is pre *aced by this reciprocating motion. It is, there • fore, very analogous is renciple to the common gar dener's roller, with which land is resamothed after haviig bees dug up.. foe sowing or ether agricultural attendee completes the ephstitu tion of cylindrical for plane surfaces, all the parts • which operate upon the cloth being of that form. Thia ingenious, engine, which was introduced into Britain from Flanders and Holland, during the per • meanies of the Hugonats, has, ;Mee its introduction and adoption here, undergone no very materiel or ,important alteration or impromment is point of theo retical principle; ass, until** exteneien of the am ton manufacture bad, Mentionni a general spirit of ' mechanical impsomoseei, had it received any.rwat ameliorationso practical execution. Two very im portant improvements have, however, since that pe riod, been introduced and adopted. The firm of .these, which originated is Lancashire, is now elromt universally employed. The second, whioh was in :vented at Glasgow, is still limited to the original proprietors or their assignees by the operation of A •pateet, the period of which, heave ern has nem nearly determined.
The scope of the former of these improvements consists. is the sehatitutien of pastelexted, in the, place of wood, in constructing three out of the five cylinders of which the engine is composed. These cylinders, when previously composed of wood, were found to be liable to two serums and important ob jection. Calendars outplayed in general business are necessarily subjected to frequent alternations and vicissitudes of heat and cold. These are entirely unavoidable, because, in smoothing or dressing cloths of the denser &beim, the effect, as. in the commas operation of ironing linens, is found to be greatly heightened. by the application of as great a degree of heat as CAD safely be communicated without dan ger to the fabrics which are to be smoothed.
The expansion of every thread which composes a given extent of cloth, although individually indistin guishable' even with microscopic aid, produces very considerable general effect, when exerted upon eight -or ten thousand of these minute cylindrical sub stances, all combined together, in the space of one tangle square yard. In this expanded state, the pressure of the calendar divests them more easily of their cylindrical form, and flattens them down until they come more closely into contact than before. This effect, which is in exact unison with the gene ad theories of expansion and contraction, will at once produce an apparent increase of closeness and density to the texture, as well as of gloss to the sur faces ; although the former is in fact deceptive, as no real acquisition of strength to the fabric can thus be obtained. The apparent density of fabric • es well
as a higher accession of gloss, are also frequently obtained by impregnating and stiffening the cloth, -after it has been bleached, with &mucilage of starch ; said this is too frequently eatriedi to a Tay wish height for the purposes of deception, which is not very amily detected, until the qioth he ;gain m. posed to moisture, when the delusive appearance is . steady vaaishes. Hence, in all dense fabrics, the adender is generally used in a heated state, whilst in thump fabrics, in which transparency, the wee more the requisite than ope ninon ie coodected with the perfectly eakt.
. The effect of theta frequent and sudden trans. done upon wooden cylinders was necessarily produc tive both of furore and warping or Issisting ; and no care in drying or seasoning the wood before turn ing could entirely remove these defects. The sub stitution of pasteboard, however, afforded a radical cum for -both, as well as a collateral advantage one iag front its being susceptible of a 'much higher de gree of superficial polish, which is always transferred to the cloth.
The paper Of •0Skisgsid cylinder, besides total exemption from all defects incidental to ligneone substances, from the immense density of which it is susceptible, by romptession, presents a superficial capable of receiving and retaining an almost lope relialed smoothness end poled?.
in order to ceastruet cylinders of this description, an axis of malleable **a and two sar£Wal PIMP Of ateteit0Aa STIN in the fiat pieces, provided. Ie dm" plates, which nmet be at least frost one to two huh dgek. there are six equidistant perforstioes nor to the arcumforauce, each capable of admitting rod of malleable inn 844 least three-fonrilis of an inch in diameter. The entire splice between the ivoOrPhSell is then to be filled with Moils pieces of the strongest pasteboard, eaceediag, by about one inch in diameter, the iron.pistm, and having etch a correspondent perforation, through which the six iron rods may pass parallel to die axis. i cylinder is thus formed, the substance of which is of pasteboard locked together by plates of iron at the extremities, and susceptible, by maw of screws on the extremities of the six connecting rods, of irk ense. cempression....-Aftes undergoing dal prepatatim. the cylinder is to to a coofteal apartment ; am as the p daily contracts, the screws are every dray tightened for the space of some weeks. The density of the cylinder is thus increased, whilst it is counicited is length ups the axis, for which contraction adequate allowance must be made in its original measure, and the operation is continued until it has gradually ac quired the requisite compression. it is then re•ex posed at the ordinary temperature of theLIir.L sphere, and by its raexpansien presents Epuu(i most inceoceivably compact, its specific gravity in this state being meter thou even that of silver... -The cooly operation now required is that of its superficial) until correctly cylindrical ; 4ad this sP a work of *mew lehour nod patience.