LEV 



LEV 



planks, like those under the eaves of 

 houses, may be made to answer the pur- 

 pose, by supporting 1 either end, until the 

 water may come to a level in every part. 

 Where works of moderate extent are 

 carried on, and where the perfect level 

 of each stratum of materials is not an ob- 

 ject of importance, the common brick- 

 layer's level, made in the form of an in- 

 verted T, thus j,, having a plumb sus- 

 pended from the top, and received in an 

 opening- at the junction of the perpendi- 

 cular with the horizontal piece, will an- 

 swer well enough. The principle on 

 which this acts, is, that as all weights 

 have a tendency to gravitate towards the 

 centre of the earth, so as the plumb 

 line is a true perpendicular, any line, 

 cutting that at right angles, must be a 

 horizontal line at the point of intersec- 

 tion. 



LEVEL, artillery foot, is in form of a 

 square, having its two legs or branches 

 of an equal length, at a juncture whereof 

 is a little hole, whence hangs a thread 

 and plummet, playing on a perpendicular 

 line in the middle of a quadrant. It is di- 

 vided into twice forty-five degrees from 

 the middle. 



This instrument may be used on other 

 occasions, by placing the ends of its two 

 branches on a plane ; for when the 

 thread plays perpendicularly over the 

 middle division of the quadrant, that plane 

 is assuredly level. To use it in gunnery, 

 place the two ends on the piece of ar- 

 tillery, which you may raise to any pro- 

 posed height, by means of the plummet, 

 whose thread will give the degree above 

 the levei. 



LEVEL, cfl?'/'e?iter*s and patioitr^s, consists 

 of a long ruler, in the middle whereof is 

 fitted, at right angles, another somewhat 

 bigger, at the top of which is fastened 

 a line, which, when it hangs over a 

 fiducial line at right angles with the 

 base, shows that the said base is horizon- 

 tal. Sometimes this level is all of one 

 board. 



LEVEL, gunner's, for levelling 1 cannons 

 and mortars, consists of a triangular brass 

 plate, about four inches high, at the bot- 

 tom of which is a portion of a circle, di- 

 vided into forty-five degrees, which num- 

 ber is sufficient for the highest elevation 

 of cannons and mortars, and for giving 

 shot the greatest range : on the centre of 

 this segment of a circle is screwed a piece 

 of brass, by means of which it may be 

 fixed or screwed at pleasure ; the end of 

 this piece of brass is made so as to serve 

 for a plummet and index, in order to 



fallow the different degrees of elevation 

 of pieces of artillery. This instrument 

 has also a brass foot, to set upon cannons 

 or mortars, so as when those pieces are 

 horizontal, the instrument will be perpen- 

 dicular. 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 de- 

 gree : this is what they call levelling the 

 piece. 



LEVEL, mason's, is composed of three 

 rules, so joined as to form an isosceles- 

 triangle, somewhat like a Roman A, at 

 the vertex whereof is fastened a thread, 

 from which hangs a plummet, that passes 

 over a fiducial line, marked in the mid- 

 dle of the base, when the thing, to 

 which the level is applied, is horizontal ; 

 but declines from the mark, when the 

 thing is lower on one side than on the 

 other. 



LEVEL, plumb or pendulum, that which 

 shews the horizontal line by means of 

 another line perpendicular to that de- 

 scribed by a plummet or pendulum. 

 This instrument consists of two legs or 

 branches, joined together at right angles, 

 whereof that which carries the thread 

 and plummet is about a foot and a half 

 long ; the thread is hung towards the top 

 of the branch. The middle of the branch 

 where the thread passes is hollow, so 

 that it may hang free every where : but 

 towards the bottom, where there is a lit- 

 tle blade of silver, whereon is drawn a 

 line perpendicular to the telescope, the 

 said cavity is covered by two pieces of 

 brass, making as it were a kind of case, 

 lest the wind should agitate the thread ; 

 for which reason the silver blade is co- 

 vered with a glass to the end, that it may 

 be seen when the thread and plummet 

 play upon the perpendicular. The tele- 

 scope is fastened to the other branch of 

 the instrument, and is about two feet 

 long ; having an hair placed horizontally 

 across the focus of the object-glass, which 

 determines the point of the level. The 

 telescope must be fitted at right angles 

 to the perpendicular. It has a ball and 

 socket, by which it is fastened to the 

 foot. 



LEVELLING. See LEVEL. 



LEVELLING staves, instruments used in 

 levelling, serving to carry the marks to 

 be observed, <?.nd at Lhe same time to mea- 

 sure the heights of those marks from the 

 ground. They usually consist each of 

 two long wooden rollers, made to slide 

 over one another, and divide into feet, 

 inches, &.c. 



