ANCHOR. Under some form or other anchors must have been as ancient as ships ; and they are accordingly mentioned by Greek and Latin authors, by whom also the invention, like many others which from clumsy begin nings have passed through different stages of improvement, is ascribed to various persons. The first anchors were probably only large stones or crooked pieces of wood loaded with heavy weights, but among the Greeks, latterly, they were made of iron ; of these the earliest had but one fluke, afterwards the other was added, and finally they were furnished with stocks. Each ship had several, of which the principal one was called lepa or sacred, and was reserved for the last extremity. This cor responds to that which has since been deno minated the 'sheet anchor.' The number of anchors carried by a ship have been finally reduced to four principal ones, all of which are disposed at the bows. These are the best and small bowers (bow yers), the sheet, and the spare anchor, and to them are added the stream and the kedge anchors, which are used for particular pur poses, and are generally carried in-board.' Every complete anchor has a ring by which it is suspended, a stack or crosspiece im mediately below the ring, a shank or perpen dicular bar, two arms proceeding in opposite directions from the lower end of the shank, a palm or fluke at the end of each arm, and a bill or peak at the end of each fluke.
When the anchor is let go in any manner from the vessel's side the heaviest end, or crown, will tend to become the lowest part, and the whole mass having reached the bot tom will most commonly fall upon the crown and on one end of the stock ; from this posi tion therefore the anchor is to be canted or turned over before it can hold. Now, it is evident that if the stock were very short, the pull of the cable would tend rather to drag the end of the stock along the bottom than to lift up one of the flukes, as must be done in cant ing the anchor ; whereas, if the stock were longer, the cable would act with increased leverage, whatever might be the length of the shank ; hence the longer the stock, within the practical limits of stowage, the more certainly will the anchor turn properly ; and, when hooked in the ground, the more powerfully will it resist any effort to overset it.
When the anchor has been turned, the stock then lying horizontally on the ground, and the point of a fluke touching the ground, it is evident that the force exerted by the ship to draw the anchor towards itself, compounded with the weight of the anchor (exclusive of the stock, and diminished by about one seventh on account of the loss of weight in produce a resultant force by which the fluke is made to enter the ground. An
anchor, when dragged; always tends to rise out of the ground, and does not again sink till it rests.
In lifting or weighing the anchor, the cable acting perpendicularly to the end of the shank, tends to break it, and hence the thickness of the shank should increase with its distance from the ring ; also the breadth of the shank should be downwards, and the like holds good of the arms, the chief dimension of which should be in the plane of the cable and shank, thus opposing the greatest strength to the greatest strain.
Besides the strains to which an anchor is exposed by its office, it is liable to accidents ; for instance, an anchor let go on a rocky bot tom has been found, on heaving it up, to have lost an arm, which was probably caused by its striking against a rock obliquelyin its descent; again, the shank has been found broken in the miciffie, though this does not seem to have been accounted for satisfactorily ; and it may here be observed generally, that the anchor de scends much more swiftly with a chain-cable than a hemp one, for the stiffness of the hemp opposes a retarding force, while the greater density of the chain adds a continually accele rating force.
The principal dimensions of the anchors in the navy may be stated shortly thus :—calling the shank 10, the arm is about 3, the breadth and depth of the palm about half this, the thickness or depth of the shank varies from •4 to •0, and the breadth about four-fifths of these, the edges being rounded. The weight of an anchor of 10 feet in length is about 11.4 cwt., and since, if the forms of all anchors were alike, the weights would be as the cubes of the lengths, the weight of any anchor might be found by multiplying the cube of its length by •0114. Thus the weight of an anchor of 14 feet in length would be x •0114=313. cwt.; the weight of this anchor is, in practice, 30 cwt., hence as far as 30 or 35 ewt., the rule is near enough, but for larger anchors it gives the result too small, because their thickness is made greater in proportion. The weight of the anchor includes that of the ring. A general rule in the navy is to allow 1 cwt. to a gun ; thus, an 80 gun ship would have an anchor weighing 80 cwt. A merchant-ship of 200 tons having an anchor weighing 10 cwt., 5 cwt. are added for every additional 100 tons ; thus, a ship of 300 tons would have an anchor of 15 cwt., and so on. Small vessels require heavier anchors in proportion than large ves sels; the sea, sudden gusts of wind, and the pull of the cable, affect the larger vessels less, and they thus preserve a steadier strain.