X.

New Method proposed for measuring a Ship's Rate of Sailing. By the same Gentleman.

A Line towing astern of a vessel, which is passing A line towed

will be a per

through the water, will pull against her head-way. As the astern of a ship ship's way increases, the pull of the line will increase; and petual log. vice versa. If this, with a proper scope of line (about 25 fathoms may probably be sufficient) shall be found to be a regulated quantity of pull corresponding in the same manner at all times to the rate of sailing, it will answer the purpose of a log. Many experiments have been made upon the same principle; but the most plain and easy one, of towing a measured length of line, has escaped trial; though less liable to give erroneous or variable results than any which can be made near a ship. By it, the rate of sailing may be obtained either constantly or occasionally, and can be taken with ease by one person: in which respect it would have great advantage over the common log, the use of which requires three persons.

By a trial made in a boat with about 20 fathoms of line, Experiment, rather larger than log line, towing astern and fastened to a spring steelyard, the strength of the pull was found to vary with the rate of sailing, which however was not ascertained by measurement; but by estimation, the boat's rate of sailing during the trial varied between 24 knots and 5 knots per hour, and the pull of the line upon the steelyards was observed to vary from 2lbs. to 5lbs. ; increasing and decreasing with the velocity. So great a variation in the strength of the pull gives all the advantage, which can be desired for forming a scale, and will allow of the experiment being made with smaller line.

If the proposed length of line is passed through a pulley The velocity so as to go clear out at the stern port or cabin window, and indicated by weights, the inner end is fastened to a loose chain, of weight adapted to the purpose, on the deck under the pulley; or to a number of small weights made consecutive by short intervals of line, the chain or weights will be drawn up more or less ac

cording

er a spring and index.

Objections, &

answers to

them.

cording to the ship's velocity. By a few comparisons of the quantity of weight raised from the deck with the rate of sailing, a scale may be marked.

In an improved state of the experiment, instead of using weights or a pulley, the inner end of the line (coming direct from the water) can be fastened to a spring, and communi- · cate with an index that shall express the rate of sailing.

This machine (if so plain a contrivance deserve that name) may be put on constant duty, or dropped occasionally to ascertain the rate.

Objections which occur, are,

1st. The line being liable to contraction or expansion as the temperature of the water varies. But it is scarcely to be supposed, that the greatest contraction or expansion of line from its mean state (after it has been properly stretched and seasoned) will occasion an alteration of a hundredth part in the force of the pull.

2d. That in a fresh wind the part of the line between the ship and the surface of the water, will be liable to some additional pull from being exposed to the wind. To this inconvenience, the log line in the common way of heaving the log is likewise exposed when the wind is much aft. In either case, when the ship is not right before the wind, the remedy is the same: which is, to throw the log or the line. over from before the lee gangway, and to give a few fathoms more of stray line; for which however, in the new method proposed, it would be necessary to apply a correction, the quantity of which may be accurately ascertained.

3d. The motion of a ship in pitching. But this is not to be regarded as an objection; for the rate of sailing is to be estimated only by what the experiment shows when the ship is going steadily; in the same manner as in taking bearings, if the compass swings, we wait till it is quiet. Whenever the ship goes steadily for ten seconds together, or even five seconds, the pull of the line will be regulated to the average rate of sailing.

XI.

Method of preventing Doors from Dragging on Carpets, or admitting Air underneath them. By Mr. JOHN TAD*.

SIR,

I HAVE taken the liberty of laying before the Society a Method of pre

model of my invention to prevent doors from dragging on venting airtight doors carpets, and to keep out the current of cold air, which en- from dragging ters under such doors as are not close to the carpets under- on carpets. neath them.

I can affix this machinery to the bottom of any door, so that the door shall pass over the carpet with ease, and, when shut, be air tight. It obviates the necessity of screw rising hinges, and is less expensive than other inventions for the same purpose.

The machinery is constructed of a slip of well seasoned beech wood, equal in length to the width of the door; this slip is one inch and a quarter wide, and half an inch thick, and to be covered with green cloth on the inside; it is to be hung to the bottom of the door with three small brass hinges, and is drawn up by a concealed spring as the door opens, and is forced down when the door shuts, by one end of it, which is semicircular, pressing upon a concave semicircular piece of hard beech wood, fastened at the bottom of the door case, and which holds it down close to the floor ór carpet, so as to exclude the air from entering under it. Hoping this invention will meet with the approbation of the Society, I remain, with respect,

Sir,

Your most humble Servant,

No. 4, Little Hermitage Street,

Wapping, Nov. 24, 1807.

JOHN TAD.

A Certificate was received from Mr. William French, Certificate of No. 280, Wapping, stating, that John Tad had fixed to its efficacy. two of his room doors the invention above mentioned, and

Trans. of the Society of Arts, vol. XXVI, p. 196. Five guineas

were voted to Mr. Tad, for this communication.

that

1

The method described.

that he found it to answer to his satisfaction, both in permitting the doors to pass clear of the carpets, and in keeping out the air.

Mr. Tad's invention consists in first cutting away the bottom of the door, so that it is about one inch and a quarter above the floor; this allows a sufficiency of room for the door to open over any carpet. To close the opening which would now be left under the door when shut, he proposes to fix beneath the door, by means of hinges, a slip of wood, of which a b d e, figs. 2 and 3, Plate II, is a section. Fig. 1 is a perspective view of the bottom of a door, with the invention annexed to it; fig. 2 is a section across the door when closed; fig. 3 is a view of the edge of the door when open; and fig. 4 is a section supposed to be made by cutting the door in two parts, edgeways. The hinges on which the slip turns, are fixed to the edge. In figs. 2 and 3, from a to b is exactly one inch and a quarter, so that when the ruler is turned down upon the hinges, it reaches the floor A A, as in fig. 2; in the other direction ad it is much less, being only half an inch, so that when it is turned up under the door, as in fig. 3, it leaves three quarters of an inch clear of the floor. It now remains to show how the ruler is turned up or down; it has always a tendency to rise up into the state of fig. 3, by the action of a steel wire spring, shown in figs. 2 and 4, which is concealed in a rebate cut in the bottom of the door; one end of the wire is screwed fast to the door at f, the other is inserted into an eye fastened into the slip at g. To throw it down into the position of figs. 2 and 4, the end h, fig. 4, of the slip farthest from the hinges of the door, is cut into a semicircle, as seen in fig. 3. When the door is just closed, this semicircle is received into a fixed concave semicircle k, fig. 3, cut in the end of a piece of wood k l, made fast to the door case; the line ml, fig. 3, represents the plane of the door when shut, and p p part of the door seen edgeways; as the door in shutting moves from p to m, the semicircular end of the slip abde presses against the end of the piece k 1, and as the door proceeds, it turns down as in fig. 2, so that by the time the door is shut, the slip is turned quite down; the edge e b of the slip is cut into a

segment

segment of a circle struck from the hinges on which it turns. The perspective view in fig. 1 shows that this contrivance, applied to any door, will not offend the eye, as it can scarcely be distinguished from an ordinary door. K, fig. 1, shows the concave semicircle of the piece of wood fastened to the doorcase, in which the semicircular end of the slip e is to be received.

XII.

Description of an improved Screw-wrench, to fit different sized Nuts, or Heads of Screws. By Mr. WILLIAM BARLOW*.

SIR,

PERMIT

ERMIT me to make a few observations on a shifting screw-wrench of my invention, which I beg leave to lay before the Society of Arts &c. through the hands of Mr. Brunel, inventor of the block machinery here.

I have found, from long experience, the imperfections of Common' the various wrenches in common use, for the screw heads screw-wrench defective. and nuts of engines in general, which are often materially injured for want of an instrument that would fit variety of sizes, and be applied with as much advantage as a solid wrench. I have had it in view to unite steadiness with conveniency in making such an instrument, and flattering myself that I have obtained both, I am desirous to communicate my invention to the Society, and have therefore sent an instrument on the principle I have actually used, and which has met with the approbation of my employers and other persons.

wrench.

This wrench, by means of a nut and screw, is adjusted An improved with the greatest ease to the exact size required, and in that state rendered so steady, that in use it is found equal to a solid wrench.

* Trans. of the Society of Arts, vol. XXVI, p. 199. Five guineas were voted to Mr. Barlow for this invention.