ELECTRICITY AND MAGNETISM:

THEIR

GENERATION AND APPLICATIONS.

A.D. 1766, June 10.-No 850.

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KNIGHT, GOWIN [GOWAN ?].-" Constructing compasses," so as to prevent them being affected by the motion of the ship," &c. "The card and box "" are made to oscillate in equal times," "by placing the centre of gravity both of the box and of the card" at proper distances "from their points of suspension," and by fixing an adjustable weight to act as a "pendulum " "to the rim "of the outward gimbol, under the axis, by which the outward gimbol may be made to move in the same time as the inward. "The inward axis or gimbol is fixed to the bottom of the box." The agate receives the point on which the needle moves, that point being attached to the needle by means of a metal "cross piece " having "small gimbols." "The agate is fixed to a slender stem of "metal, the lower end of which is pointed," and turns freely in "a hollow sockett." "The sockett is fixt as a pedestal in the " centre of the bottom of the box, and has a slit on one side," to admit a pendulum screwed to the lower part of the stem. When "the box is in motion," the pendulum, "stem, and agate will move "to and fro."

Also, "constructing the variation compass," "for taking the sun's "azimuth and amplitude, and the bearing of distant objects." A moveable "mirroir is placed at each end of the index, just behind "the sights," "so as to reflect ""the graduated rim of the card, "which will then appear to the eye" vertical, and cut by the "thread of the opposite sight," which also cuts the object. "In taking the sun's azimuth," when its height is considerable, "the rays of the sun are reflected from a small polished cylander placed "behind the sights and an opening is made in each end of the

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"index bar, that the brass rim may be reflected without interruption "from the bar, which is slit that the shadow of a thread underneath "it may cut the graduated rim of the card."

[Printed, 3d. See Rolls Chapel Reports, 6th Report, p. 159.]

A.D. 1779, June 25.-N° 1229.

WRIGHT, GABRIEL.-"A new-constructed azimuth and amplitude compass."

"The new-invented parts" and "improvements" consist of:"A horizontal nonius (or verniers) division," "having a vertical "motion" by means of a nut outside the compass box.

An "index and sights, which goes on the compass box," used when the sun's azimuth or amplitude is taken. Two "mirrours" are "placed at right angles to each other on the plane of the index;" also " 'a screen or dy'd glass," and "a convex glass." "To the "vertical sight" "is fixed a horizontal one," "to look down on "the reflecting glasses &c. to view the sun & the horizon of the sea and to read of the degrees from the card &c. thro' the convex glass." "At the other end of the index " is placed a weight" to ballance the whole."

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Also an improved "reflecting quadrant or octant, having the following new parts":

"A round plate" (with "a hole," "a circular slit,” and “a "milled edge"), " carrying the index glass," and moving round the centre of the index, adjusted by a 'clamp & screw;" "a "horizontal screw" adjusts the index glass to the horizontal glass. The index glass has a horizontal fine hair line.

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A piece of brass is screwed to the quadrant frame, having “a fine "division cut on it" and adjusted "to coinside with a like division "cut on the edge of the round plate."

A “sight_vane,” “having a piece of thin brass with a hole in "the center," sliding up and down in a "slit," "so as to view objects "in the true plane of the quadrant.”

"A brass frame," carrying a hair line, which sometimes takes the place of the sight vane.

A "sight vane," with two lines drawn across the inside ("used "with the compass in taking the sun's azimuth and altitude at the same time"), is "fastened to the arch of the quadrant.”

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A reflecting glass," to view objects from 140 to 180 degrees apart.

"A cylindric box with two parallel glass sides," filled with a liquid that will float a hair (attached to a cork and weight) vertically, "to level the compass by when the horizon of the sea cannot be "observed."

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Printed, ed. See Rolls Chapel Reports, 6th Report, p. 164.]

A.D. 1782, February 5.-N° 1318.

NAIRNE, EDWARD.-This invention is stated in the title to be, a "New-invented and most usefull improvement in the common electrical machine (which I call the insulated medical electrical machine), by insulating the whole in a particular manner, and constructing the conductors so that either shocks or sparks may "be received from them." The "form to be excited" of this electrical machine is "supported immediately on non-conducting “substances.” “The conductor or conductors which either give " to or receive the electrical fire from the excited part, is composed " of a coated electrical jar or jars or any other substance than " [that?]" can receive a charge of electricity or a conducting sub"stance connected with them." Connected with these "con"ductors" are "tubes" or "rods," with ball and socket joint or joints, that will conduct electricity, to direct the electric discharge to any part of the body required; and by these means shocks are given by discharging the electricity (either by metallic connection with the earth, or with the conductor of the opposite kind of electricity) when at some distance from the part through which the shock is to be sent; if sparks are required the distance is lessened.

By means of the " conductors" and jointed "tubes," the human body can be in any part affected with either kind of electricity in any convenient manner.

[Printed, 3d. See Repertory of Arts, vol. 7, p. 380.]

A.D. 1782, March 20.-N° 1322.

HERIOT, JAMES.-A "New invented mariners compass, with compass boxes or bittacles, pendent or standing, with ventilator, " to contain either lamp or candle, as occasion may require, calcu"lated to obviate every difficulty which those of late use have been subject to, for the purpose of navigating all kinds of ships " or vessels."

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No Specification enrolled.]

A.D. 1788, August 12.-N° 1663.

MCCULLOCH, KENNETH.-"A mariner's compass on a new "construction."

An "azimuth compass " is described and shown, in which gimbals are dispensed with. The "compass vessell" is supported on a pivot at its centre of gravity, which is brought as near as possible to that of the needle; the needle moves upon a point

a small distance above the centre of gravity," and near to the centre of motion on which the compass vessel is free to move. For this purpose the bottom of the compass vessel "rises in a "conical form," is supported upon a prop" free to turn in the outer case of the instrument, and has "a ring of lead" round its bottom "to ballance" it; two arms, with slits, in which "pivets" are free to traverse up and down, spring from the prop and turn with it when necessary; the pivots are fixed to the compass vessel "in a line with the thin metal plate on which the pivot of the "needle rests." The needle is "bent so that the point of the pivot" "is a small distance above the centre of gravity." Besides the above, the compass is fitted with an azimuth circle round the edge of the card, a nonius stop with a slide passing through one of the pivots, a metal bar carrying a magnifying glass to read the divisions of the azimuth circle, and "sight vaines."

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A "steering compass" on the same principle as the azimuth compass, is described and shown, having the arms with slits, and the prop screwed into the outer case.

Another compass is described and shown. The compass vessel is supported by "jambols," and the inverted cone in which the needle pivot rests has a weight attached to it mounted in small "jambols." The smaller gimbals are supported by standards rising from the bottom of the compass vessel. In this compass all the centres of motion are as nearly as possible in "the same "horizontal plain.”

[Printed, 6d. See Rolls Chapel Reports, 6th Report, p. 144.]

A.D. 1791, July 5.-N° 1815.

WRIGHT, GABRIEL.-A new method of making mariners' compasses.

A "gimbel compass" is described and shown, in which the "inside compass box or kettle," made of wood or any metal except