TOOLS AND INSTRUMENTS. 



183 



triangular or diamond-shaped piece of zinc is 

 neatly let in; the end T-rod has the cross-piece 

 shaped in a rounded form and painted white. 



Fig. 215.— Borning-rods. 



Ground Compasses. — These are useful in mak- 

 ing geometrical flower-gardens or striking beds 

 on lawns. They are constructed on the same 

 principle as the common compasses, with the 

 segment gauge used by mechanics. The legs 

 are made of hard wood, 5 or 6 feet in length, 

 and shod with iron. Instead of a segment, a 

 straight plate of sheet-iron, about 1^ inch broad, 

 may be used, with a space cut out along the 

 middle, through which the end of a fixed screw 

 on each leg may pass; then, by means of two 

 thumb-screws, the legs can be secured at any 

 required distance apart. In many cases where 

 the above may be employed to describe circles, 

 or circular parts, a sort of beam compasses may 

 be substituted. Such may be formed of a piece 

 of inch-thick deal board, 2| inches wide and 

 10 feet in length, with a slit along the middle to 

 within about 6 inches of each end, to admit of a 

 screw ^ inch in diameter passing through and 

 along. There should be two screws, their lower 

 ends being pointed. The length of each screw 

 may be 18 inches, and each should be furnished 

 with two nuts and two washers. Supposing it 

 may be required to have the beam raised about 

 6 inches above the points, in order to clear any 

 inequalities of surface which it may have to pass 

 over, screw up the nuts, so that the under side 

 of the beam may rest upon them at the above 

 height ; then screw down the nuts on the upper 

 side of the beam, but only one of them tightly, 

 until the other screw is moved along the slit, so 



that the points may be at the required distance 

 apart; and when this is ascertained to be the 

 case, let the other nut be likewise screwed down, 

 in order that a line may be traced without the 

 points being moved from the true distance in 

 the course of the operation. As this instrument 

 can be adjusted so that the points may be se- 

 curely fixed at any width, within certain limits, 

 and as the beam can be raised more or less, it 

 may be used as a gauge for the breadth of walks, 

 or other distances between two points. 



The Plummet may be very usefully employed 

 in placing objects correctly upright, such as 

 posts, stakes, and trees. The plummet should 

 be formed with a conical point, and this point 

 should be exactly in the line of suspension, so 

 that when the cord suspending the plummet is 

 held in line with a row of stakes, for instance, 

 the point will touch or indicate the spot where 

 another stake should be driven. 



Levels. — Wherever walks, roads, or drains are 

 to be made, or indeed whenever grounds are to 

 be laid out, a level is indispensable. Though the 

 surface of the ground may, to all appearance, be 

 quite level, yet it will often be found, when the 

 level is used, to slope considerably. Where walks 

 run near the bases of walls, or other buildings 

 where there are long horizontal lines, nothing 

 can look more unsightly than an uneven sur- 

 face ; for all its irregularities are made more ap- 

 parent by the horizontal lines of the building. 



There are many different kinds of levels. The 

 common level (fig. 216), used by bricklayers and 



Fig. 216.— Level. 



carpenters, is well known; it merely consists of 

 a straight bar of wood, with another bar placed 

 at right angles to it, and from the centre of 

 which is suspended a plumb-bob and line. The 

 level seen in fiV. 217 is used not onlv for forming 

 a horizontal surface, but also for ascertaining 

 whether an object is truly perpendicular or not. 

 The artillery foot-level (fig. 218) has a line and 

 plummet, and a scale of 90° between the two 

 legs. When the plummet hangs in the middle 

 of the scale, the feet rest on a level surface, 

 otherwise one foot must be raised, and the 

 degree of acclivity or of descent will be shown 



