(2) Dew-retting is thus conducted. The pulled stems are allowed to stand in the stooks for 3-3 days, and are then spread out carefully on the grass. Here they are subjected to the effect of showers and dews, and an occasional watering if necessary, for a period which may extend to 6 weeks, care being taken to turn them constantly during the whole time. The appearance of pink spots on the stems must be watched for, whereupon the stems are gathered up, tied in bundles, and piled in stooks, to dry. By this method, the most valuable white hemp is produced ; but the opera tion is very tedious, and entails great expenditure for labour.
(3) Snow-retting is sometimes practised in Russia and Sweden. After the first snow-fall, the dried hemp-stems are spread out, and left to be covered by subsequent falls, till the spring, when they are generally found to be sufficiently retted.
Grassing and Drying.—After water-retting, the hemp is removed from the water to a field of grass which is clean and unused by cattle. Here it is spread out evenly, and allowed to lie for 3 weeks or more, to bleach, and to enable the fihre to free itself; during this time, it is turned over, with long light poles, every 3-4 days. The process is considered complete when pink spots com mence to appear on the stems. Drying is sometimes effected by exposure on walls or rocky ground, sometimes artificially in ovens. When dry, the stems are again tied up in bundles, and carried to a barn or rick.
Breaking and Scutching.—So close a resemblance exists between hemp and flax stems, that the machinery devised for the treatment of the latter is equally applicable to the former, always allowing sufficient strength to over come the superior toughness of the hemp stems. Flax being of greater importance than hemp in our manu factures, breaking and scotching machines suitable to both are de scribed under the head of the former (see p. 969). A peculiar hemp breaker, devised by G. M. Mure, of Turin, is shown in Fig. 650. Be tween two rims carried by the shaft A, are 4 grooved rotating rollers B ; behind the table m, are placed a number of grooved boards or plates, loosely connected with each other, and made to follow the periphery of the arc C. While putting stems upon the feeding board, the hand is protected by the grating 1. The stems pass along the arc C, and are pressed against the grooves of the latter by the rollers B, through the rotation of A. A counter pressure by C against the beater B is produced by the lever D and weight E.
Characters and Uses of the Fibre.—A section of a portion• of the stem of the hemp plant, magnified 100 times, is shown in Fig. 651 : a is the cortical portion ; b, the ligneous ; e, the epidermis ; f the bast fibres, which are divided into two zones, z' z'. The fibres of the first zone are solid and poly gonal, and boar some analogy to those of flax ; those of the second zone are rounded, but irregular, contorted, and encroaching upon each other. Their walls too are relatively thinner, and the internal cavity is very large. The differences are more clearly seen in Fig. 652. a. a'. Under test H, the fibres z' z' exhibit the remarkable characteristic of assuming a full blue colour, surrounded by a distinct yellow margin.
Fig. 652, mag. 300, repre sents the fibres : a a', sec tions of groups of fibres of the first and second zone , respectively ; b, fibres seen longitudinally ; c, ends. Ex endued by test F, the fibrous bundles assume a blue or violet tint ; often they approach a greenish hue, passing more or less to yellow at the edges. This last coloration arises from a yellow envelope, entirely covering the fibre, and disappearing only after complete bleaching. The isolated fibres are slightly transparent, and of very irregular diameter, even in short lengths ; their surface is sometimes even and smooth, sometimes striated or corrugated longitudinally ; they are often fiat and ribbon-like. Numbers of nearly black, but ex tremely fine, transverse lines aro visible ; another peculiarity is an abun dance of irregular fibrils, detached from the body of the fibre, after repeated friction. The sions of the fibres of hemp vary greatly ; in the case of European hemp, the length may be set down at in., mean, 0.866 in. ; and the dia meter at in., mean, 0.00066 in. Hemp, as it occurs iu the market, is longer, more rigid, and coarser than flax ; it forms ribbons, more or less wide, and of varied colours—straw-tint, nearly white, green, brown, deep•grey, and nearly black, according to the manner in which it has been dressed and dried. Samples of the fibre, exposed for 2 hours to steam at 2 atmos., boiled in water for 3 hours, and again steamed for 4 hours, lost ou the average as follows :—Italian hemp, per cent. ; Russian hemp, per cent. Under similar conditions, flax lost 3.50 ; Manilla hemp, 6.07 ; Phormium, ; eoir, Hemp is employed almost exclusively in the manufacture of ropes, twine, and nets (see Rope).