Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/16

6 used, the service for which they are intended being generally performed by the aid of a steam-tug vessel. The tables on pp. 4 and 5 give the sizes and number of anchors and cables carried by ships of the Royal Navy, and those required by Lloyd's rules to be carried in merchant ships. The sheet and bower anchors are of the same size, and are given in the tables under the heading “Bower.”

Public attention having been directed to the subject of anchors by the specimens which were exhibited at the Exhibition of 1851, a committee was appointed by the Admiralty in the succeeding year to consider and report upon the qualifications of the various kinds. The committee determined the qualities it was desirable for an anchor to possess, and assigned numerical values to each. The following tables give the result of their labours, showing the number of marks obtained by each anchor under trial:—

Note.—This Table only professes to show approximate values, and has no pretensions to mathematical accuracy or precision.

The following is a recapitulation of the order in which the anchors were ranked by the committee, together with their relative percentage of inferiority or superiority in the Admiralty anchor, the value of which, as given in the foregoing table (18·17), was taken as the standard or unit:—

The decisions of the committee have been much questioned, one of the objections being that the qualities of strength and holding on, neither of which is of any use without the other, were assigned such different values as 15 and 80; it has also been stated that the Admiralty anchor was treated unfairly, as one was taken promiscuously out of store for the trial, whereas the other competing anchors were made specially for it. The Admiralty anchor (fig. 2) differs only from the ordinary anchor in having a nut, a, worked on the square, so that a wooden stock may he ﬁtted temporarily if the iron stock is damaged, and that its proportions and form have been carefully considered and deﬁnitely ﬁxed. Lenox's and Aylen's were modifications of the Admiralty anchor. Mitcheson's was of a difficult section to forge, and consequently expensive, and was withdrawn from the test of strength. Isaac's was of a peculiar construction, and may be passed over as more curious than useful.

Rodger's anchor, placed second on the list, was one of Captain Rodger's, R.N., who for the last forty years has devoted considerable pains to the improvement of anchors. Among his earlier inventions is an anchor with a hollow shank, to obtain greater strength with a given weight of iron; then an anchor without a palm, which he termed a “pickaxe anchor;” afterwards a “small-palmed” anchor; and by a patent taken in 1863, an “indented small-palmed anchor” (ﬁgs. 3 and 7). The stock is of iron in large as well as small anchors, and is made with a mortice, to fit over the shank instead of passing through it. It is somewhat heavier than the stocks of other anchors; the arms are shorter than usual in proportion to the length of the shank, and are of a wedge shape, varying in sharpness from the throat to the head of the palms; the back part of the arms is parallel from palm to palm; the palm is double concave on the front, and has a small border at the edge for confining the soil through which it is dragged; it also has a large indentation on the back for the same purpose and to save weight; the shank is rectangular at its junction with the arms, and square close to the collar for the stock; the crown is made longer than usual, and has a large countersunk hole in its centre to save weight. 11 is claimed for this anchor that the peculiar form of the palms and arms, with the hole in the crown, give it great holding power, and that it will bury itself in the soil until the upper palm is beneath the surface, and consequently is not liable to be fouled by the cable.

. 5.—Trotman's anchor.

Trotman's anchor (fig. 5), which obtained the highest place in the committee's estimation, was an improved Honiball's (Porter's). The stock is of iron, similar to the Admiralty anchor; the shank is of rectangular section, somewhat larger in the centre than at the ends, and is made fork-shaped at one end to receive the arms; the arms are in one piece, and are connected to the shank by a bolt passing through their centre. The peculiarity of the anchor is that the arms pivot about this bolt, so that when it takes hold the upper fluke is brought in contact with the shank, thus reducing the height above ground, and rendering it almost impossible for the cable to get entangled round it, or, in other words, for the anchor to become foul.

Of the anchors tested by the committee, Trotman's,