Description of Instrument for boring holes in Granite, Sc.

BY MR. J. TRESIDDER, GWENNAP.

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THIS instrument consists of a frame supporting two borers, which are alternately raised by two sets of three arms, radiating from and symmetrically arranged round an axis, which is turned by a winch handle. The arms raise the borers by bearing against a collar which is fixed to the middle of each, as represented in the wood-cut, fig. 1, and at the same time turn them. This turning motion is effected by the points of the arms or cams entering the radiating grooves in the under-side of the collars, when they are in a direction at right angles to the motion of the arms; the points relieving themselves by drawing the grooves round in the direction of their own motion. This will be more

b

a

Fig. 1.

easily understood by fig. 2, which shows at a the point of the arm as it enters, and at b, as it leaves the groove in the collar. The springs at the end of borers are intended to project them forward against the stone which is to be bored when the holes are to be made in the horizontal direction; or in any oblique position in which the weight of the borers is not sufficient for the purpose.

Fig. 2.

The instrument is not a perfect one; but the judges at the annual exhibition considered the idea good, and that it could be modified so as, in many cases, to be made a useful and simple tool. Probably it would be improved by having the collars, springs, &c., fixed to iron tubes, into which borers of any length could be readily inserted, and held by screws or cutters. As the hole deepened, the same arrangement would easily admit of the necessary adjustments.

Improved Screw Propeller for Steam Vessels.

BY ALEXANDER MOORE, Esq., H. M. DOCK YARD, DEVONPORT.

THIS propeller is composed of two precisely similar parts which dovetail together, as delineated in the annexed figures, and is considered to possess the following advantages:—

First. In the event of one of the blades being broken by striking against any object, or being injured by a shot, the

fractured half can be replaced without destroying the whole propeller, and consequently a very considerable saving would be effected in making good the damage.

Second. It can be taken to pieces and stowed in any convenient part of the hold, instead of being placed on the weather deck, thereby relieving the ship of top-hamper, and reducing the quantity of ballast necessary for her stability.

Third. In the event of its being necessary to ship the spare propeller, with which it is proposed each ship should be provided, it can be transported along the deck in two pieces with much greater facility than in one. The drawing represents one weighing about five tons.

Fourth. Should one-half of the propeller be broken in a foreign port, the other half can be used as a model for casting a new one-the two halves being in shape exactly similar.

Fifth. It can be put together in a very short space of time; and from the manner in which it is secured by dovetails and steel keys (the latter being capped over to prevent galvanic action), with a small increase of metal about the "boss," will be found to possess the requisite strength.

Description of the engraving. Scale, one-eighth of an inch to a foot. Fig. 1. Transverse section of screw put together. Fig. 2. Transverse section of the screw, separated, showing the dovetails, c, c. Fig. 3. Longitudinal view of the screw put together. Fig. 4. Longitudinal view of screw separated. a, a, a, steel keys protected from galvanic action by brass caps filled with grease, and secured by screws. b, b, brass rings let in flush with the surface.

Portable Sketching Easel.

BY MR. F. W. HARVEY, ORIEL-STREET, OXFORD.

THE sketching easel, by Mr. Harvey is considered to surpass all that have yet been offered to the public, and combines lightness, portability, steadiness, strength, and completeness. It contains a seat, brush, pencil, and colour-box, two strainers for paper or canvass, with box for loose sketches, and an easel-frame capable of being used as a table when required. The whole weighs about seven pounds. The seat will bear three hundred weight, and the easel-frame thirty pounds.

Fig. 1, shows its appearance when open for use, and fig. 2, when closed for convenience of carriage.

The size, when closed, is 22 ins. by 12 ins. The inventor manufactures it in Spanish mahogany, and fitted with a German silver water-bottle, two strainers, 15 ins. by 11 ins., covered with calico, and a white enamelled copper palette.

Improved Whim.

BY MR. JOHN MAYNARD, MINER, ILLOGAN,

To prevent the accidents which not unfrequently occur, both to men and horses, through the running of whims, it is proposed to fix a drag to the shaft of the whim, to be acted upon by a lever conveyed through a pipe or launder, under ground, to the landing brace or place, with a handle, by which, if the load runs away with the horse, or any other accident occurs, the lander may immediately stop the whim. As the driver is usually afraid to run out of the whim-round, and generally throws himself on the ground, it is suggested that another lever should be placed near the shaft of the whim for the driver to assist the exertions of the lander.

Improved Miners' Quadrant, with Telescope attached.

BY MR. W. WILTON, ST. Day.

THE principal advantage in this instrument over Mr. Wilton's centre quadrant is in its great simplicity. The telescope is attached to the side of the dial, and may be used at the same time with the common sights, the line of sight through the telescope being always parallel with the common sights of the dial. It gives the vertical angle to one minute, and the horizontal angle to two minutes, and also the feet and inches of the underlie and perpendicular to every fathom of the slant line. When used with the improved dial it is equal for all serviceable purposes to the land surveyor's theodolite. It is so constructed that the telescope attached to the quadrant may be easily removed, and a pair of common sights are supplied with the instrument to be used for underground purposes, the telescope being principally intended for surface work.