Page:The American Cyclopædia (1879) Volume I.djvu/497

 ANCHOR 465 a horizontal instead of a vertical position ; the square is the square end of the shank, which at the extreme end, just beyond the place where the stock is fastened, is bored through for attach- ing the shackle by means of a pin ; the shackle is a ring, by means of which the cable or chain is attached to the anchor ; the crown is the extreme end of the shank, or the external part of the arms, on which the anchor falls when let go in a vertical position ; the palms or flukes are parts of the arms, of a shield-like form, which are near their extremities, and constitute the holding surface of the anchor. The angle of the face of the palm with the shank is 51. The arms extend from the shank in a curve the outside radius of which is 35. That part of each arm which sustains the palm is called the blade, and the part which projects beyond the palm, and has to open the ground, is named the point, peak, or bill. If 100 be taken as the unit of length for both the stock and shank, then 40 will represent the average length of each arm from the crown to the bill. The relative weights of these several parts may be roughly estimated as follows: The shank, T 5 ^ of the whole; each arm, T 3 ^; two palms, Y 1 ^; stock, ; shackle, -^ When an anchor is let go from the ship, it falls ver- tically through the water, and, should the bot- tom be an even one, the crown will strike first ; but a rocky bed may compel one of the arms to receive the full force of the fall, for which reason any cross section of an arm should rep- resent an ellipse, with the line of its greatest diameter vertical to the point of probable con- tact, thus receiving the heaviest strain in the direction of the greatest strength. After striking the ground the anchor falls sideways, the arms lie flat, and the stock rests on one end. A length of chain proportional to the depth of water, and so calculated that the hardest pull of the vessel will not lift it en- tirely from the ground, is permitted to run out. The action of the current or of the wind on the vessel soon makes her exert a traction on the chain, and this lying on the ground pulls down the shackle, bringing the stock flat on the bot- tom, and the arms perpendicular to it; this is called canting the anchor. The longer the stock and the shorter the arms, the less force will be required to perform this opera- tion ; hence in all anchors the stock is longer than the arms. After canting, the anchor will be dragged or will hold. Quick holding de- pends on the sharpness of the bill and the angle of the palm with the ground. For " weighing anchor," the chain or cable is taken in by aid of a capstan, till the bow of the vessel is brought over the shackle ; here an in- creased pull is necessary to trip it, and the anchor is raised to its place. The property of quick tripping depends on the curve of the arm, and on the angle of the palm ; they have to be such that when the shackle is pufled up vertically, the bill cuts open a short curved circular way in which the palm and arm fol- 31 VOL. i. 31 low. When the palm is out, the ground is torn open by the arm, which is comparatively sharp, and acts with a more advantageous lev- erage than the palm would. More than two thirds of the ruptures of anchors happen in the operation of weighing. We have said that the arms ought to be thicker in the dimension parallel to the shank, to resist shocks against rocks. The same is necessary to resist the strain in tripping. The shank is exactly in the same circumstances, and has to be thicker in the direction of the arms, and to decrease in size from the crown to the square. Though theory indicates rectangular sections as best for the arms and shank, they are in practice made round or oval, or at least the angles are much rounded. This has been found necessary for the preservation of cables, which often take a turn around the anchor when the vessel changes its direction with the tide or wind. The forg- ing of an anchor requires the constant super- intendence of an educated engineer, while the workmen should be chosen with an eye to their skill and judgment, as well as muscular strength. A sufficient number of wrought-iron bars made from the best scrap iron, or from " Welsh mine iron," are bound together by iron hoops, form- ing the faggot; this is placed in a specially contrived furnace, where it is brought to a white or welding heat, when it is removed by the aid of a crane to the anvil, and subjected to the rapid and powerful blows of the stamp- ing hammer. When an approximate form is thus obtained, the finishing is done by heavy sledges in the hands of the anchor smiths. The arms and stock may be forged separately and then welded together at the crown, or, as in the process patented by Mr. Perrins of England, the whole may be built up by the welding to- gether in a given order of a number of separate pieces, so adjusted as to secure the greatest strength in the direction of the heaviest strain. When the* stock is of wood, it consists of two beams, generally oak, mortised in the centre so that they may embrace the square, upon which they are firmly bolted; the middle thickness should be one twelfth of the length, and the whole should taper from the centre out, the diameter of the end being about one half that at the centre. The iron stock, which is rapidly replacing that of wood, is a simple round bar tipped with knobs, which prevent its en- tering the ground, and with one end bent at right angles. This passes through a hole in the square which is rounded out for the pur- pose, and is held in position by a metal ring or shoulder upon one side, and a slit and key on the other; by removing this key, the whole stock may be driven through, and thus, owing to the crook upon the end, be doubled down upon the shank, rendering it much more com- pact and portable. So important is the quality of strength in an anchor, that all modifications of the tried and approved form, or any im- provements that have the appearance of sac- rificing strength to convenience in handling,