the centre, where the square of the anchor is let into the stock, have induced me to offer to the Society of Arts &c. a plan of an anchor, which may be cheaper in construction, and more likely to hold in various situations than those in

common use.

ens them and

The model I have sent will sufficeintly explain my in- The improve. tention, and show how beneficial it may be in strengthening ment strength the anchor stocks. I wish much to notice to you its pro- makes them bability of holding in the ground longer than other anchors, hold better. on account of the additional weight of the stock; and this will more particularly be the case in banks which shelve suddenly down from the shore, such as at St. Helena, Cawsand Bay, and indeed in most of the islands in the West Indies. The proportion of additional iron, as explained by my model, is in all anchors to be twice and a half the diameter of the shank from each side at the stock, and of course this mode will supply the place of the present nuts, which are only intended to prevent the stock from slipping in and out, whenever it becomes loose, which accident anchors are very liable to in hot climates. My anchor stocks will save a considerable quantity of the finest timber, and give much greater security.

ble to happe

in fishing a

I likewise beg leave to offer to the Society a model of a Accidents liadouble fish hook, for the purpose of fishing the anchor, an operation which, in the common mode of doing it, is fre- chors quently attended with accidents both to the ship and crew, from the anchor suddenly slipping unexpectedly in raising it to its proper position.

I flatter myself that these improvements will meet with the Society's approbation.

I am, Sir,

Your most obedient humble Servant,

Lower Mitcham,

Feb. 13, 1808.

H. L. BALL.

This anchor, in external appearance, differs very little The anchor from the common anchor; the improvement consists in the described. forming and fixing of the shank of the anchor to the stock. The stock a a, Pl. I. figs. 6 and 7, is made of two pieces of oak bolted together, and well secured by hoops. In the com

mon

Improved me

mon method, in order to prevent the anchor stock from slipping off the shank, a square projection b b, fig. 8, is forged upon the shank; this is improved by Captain Ball, as shown in fig. 6, where this projection d d is extended on each side of the shank, far enough to receive two bolts through each of these extensions, which bolts hold firmly together the two pieces of timber that form the stock, and secure the stock fast to the shank. Two iron hoops, fig. 7, ee, are driven on the stock between the bolts, and ƒƒƒƒ are other hoops, and gggg are treenails to strengthen the whole.

Fig. 4, represents Captain Ball's method of fishing an thod of fishing anchor. Fig. 5 shows an enlarged view of his double hooks

the anchor.

used for this

purpose.

In the usual operation of heaving an anchor, it is drawn up by the cable until it appears above water: the cable will not now raise it higher, it is therefore bowsed up by the cat block a, fig. 4, from the cat head b, the cable d being slackened out as it rises. When it is got up as high as the cat block will raise it, a strong hook, called the fish hook, fastened to a rope e, which is suspended by a tackle from the shrouds, is hooked to the anchor at the bottom of the shank, and thus the arms of the anchor are elevated above the stock, until one of the flukes is brought up to the timber heads ff, to which it is made fast by a rope and chain, called the shank painter. In this operation the fish hook sometimes slips and occasions mischief, to remedy which, Captain Ball has applied two hooks instead of one, which keep firmer hold. These hooks are shown upon an enlarged scale at g g fig. 5, attached to the rope e; each of these hooks takes one of the arms of the anchor, close to the shank, and holds it firmly. i i are two small lines made fast to the hooks, to direct them so as to get proper hold of the anchor.

IX.

Observations on the Progress of Bodies floating in a Stream: with an Account of some Experiments made in the River Thames, with a View to discover a Method for ascertaining the Direction of Currents. By JAMES BURNEY, Esq.

HAVING

flot down a stream faster

rent.

AVING frequently noticed, that the heavy craft on Heavy bodies the River Thames, during a calm and without the assi ance of oars or of towing, made a progress faster than the than the cur stream of the tide on the surface, it led me to make inquiry as well into the fact as concerning the cause, and gave rise to some experiments, which, with the ideas they suggested, are here set down; no otherwise according to method than being in the order they occurred.

light ones.

On questioning the men belonging to several barges, Laden barges which, unaided by wind, oar, or towing, were floating with fat faster than and overtaking the stream, they all agreed in the general fact, as a circumstance familiar to them. They said likewise, that a laden barge made greater progress than a light barge; and this was corroborated by the evidence of the boats attached to them being drawn after them; for the barges overtook the moving water so fast as to have good steerage way. They attributed the difference in favour of a laden barge, to her having (as they expressed it) more. hold of the tide than a light barge: by which it appears, that they supposed the stream of the tide was stronger underneath than on the surface. Adhesion to the atmosphere may retard the surface, except when the current of the atmosphere (the wind) goes in the same direction with the current of the tide; and then it may occasion an acceleration.

Monday, July the 18th, I went on board a barge half This is not ow laden, which was floating down the river, but with steerage ing to a more rapid under way, between Putney and Chelsea bridges. I conjectured current, the rate of the tide to be a mile and a half per hour: there was a very light air of wind in a direction contrary to the

VOL. XXIV-SEPT. 1809.

E

stream