Level

an instrument to draw a line parallel to the horizon, whereby the difference of ascent or descent between several places may be found, for conveying water, draining fens, . Air - Level , that which shews the line of level by means of a bubble of air, inclosed with some liquor in a gla tube of an indeterminate length and thickne , whose two ends are hermetically sealed. When the bubble fixes itself at a certain mark, made exactly in the centre of the tube, the plane or ruler wherein it is fixed is level; when it is not level, the bubble will rise to one end. This gla tube may be set in another of bra , having an aperture in the middle, whence the bubble of air may be observed. There is one of these instruments with sights, being an improvement upon the last described, which by the addition of more apparatus, becomes more commodious and exact: it consists of an air-level about eight inches long, and 7 or 8 lines in diameter, set in a bra tube, with an aperture in the middle: the tubes are carried in a strong straight ruler, a foot long, at whose ends are fixed two sights, exactly perpendicular to the tubes, and of an equal height, having a square hole, formed by two fillets of bra cro ing each other at right angles, in the middle whereof is drilled a very little hole, through which a point on a level with the instrument is described: the bra tube is fastened on the ruler by means of two screws, one whereof serves to raise or depre the tube at pleasure, for bringing it towards a level. The top of the ball and socket is riveted to a little ruler that springs, one end whereof is fastened with screws to the great ruler, and at the other end is a screw serving to raise and depre the instrument when nearly level. Artillery foot - Level , is in form of a square, having its two branches or legs of an equal length, at the angle of which is a small hole, whence hang a line and plummet, playing on a perpendicular line in the middle of a quadrant: it is divided into twice 45 degrees from the middle. Gunner’s - Level , for levelling pieces of artillery, consists of a triangular bra plate, about 4 inches, at the bottom of which is a portion of a circle divided into 45 degrees; which angle is sufficient for the highest elevation of cannons, mortars, and howitzers, and for giving shot and shells the greatest range: on the centre of this segment of a circle is screwed a piece of bra , by means of which it may be fixed or screwed at pleasure; the end of this piece of bra is made so as to serve for a plummet and index, in order to shew the different degrees of elevation of pieces of artillery. This instrument has also a bra foot, to act upon cannon or mortars, so that when these pieces are horizontal, the instrument will be perpendicular. The foot of this instrument is to be placed on the piece to be elevated, in such a manner, as that the point of the plummet may fall on the proper degree, . The most curious instrument for the use of the artillerist, was lately invented by the very ingenious colonel Congreve, of the British artillery; having the following qualifications, viz. 1. It will find the inclination of any plane, whether above or below the horizon. 2. By applying it either to the cylinder, or outside of any piece of ordnance, angles of elevation or depre ion may be given to the 60th part of a degree, with le trouble than the common gunner’s quadrant, which only gives to the 4th part of a degree. 3. It will give the line of direction for laying either guns or mortars to an object above or below the horizon. 4. It will find the centre of metals of any piece of ordnance. 5. With it, a point may be found in the rear of a mortar-bed, in the vertical plane of the mortar’s axis; consequently a longer line of sight is given for directing them to the object than the usual way. 6. It answers all the purposes of a pair of callipers, with the advantage of knowing (to the 100th part of an inch) diameters, whether concave or convex, without the trouble of laying the claws upon a diagonal scale. 7. On the sides of the instrument are the following lines, viz. equal parts, solids, plains, and polygons, logarithms, tangents, versed sines, and numbers, plotting scales, and diagonal scale of inches for cutting fuzes by. 8. In the lid of the instrument-case is a pendulum to vibrate half seconds. It is likewise of singular use in surveying; as, 1. It takes horizontal angles to the 60th part of a degree. 2. Vertical angles. 3. Levels. 4. Solves right angled plane triangles. 5. Oblique-angled plane triangles. 6. Answers all the purposes of a protractor, with the advantage of laying down angles exactly as taken in the field. N. B. captain Jordane’s ingenious instrument answers nearly the same purposes. Spirit - Level . See Air Level . By the term level is also to be understood the line of direction in which any mi ive weapon is aimed.