SOUTHERN CULTIVATOR. 
309 
to four or five feet, because three is a common measure of 
both 13 and I5, which are the ordinary strides of the 
rafter levels. And so the compass level can be used with 
great convenience in connection with levels of 13 and of 
15 feet stride.) The other parts are (see Fig. 1.) a, a flat 
circular piece of pewter inches in diameter, of an 
nch thick; a piece of brass hooping 1 1 inches long 
tapered off at one end. and an inch wide at the other end. 
(These parts, a and b, are connected with each other) ; c 
a graduated scale. Mine is divided into 24 parts — 12 on 
each side from the centre, o. Nov/ see Fig. 2. It repre- 
iFtg. 2 .) 
sents the parts, a and b of Fig. 1 — the letters of the two 
figures correspond with each other. It also shows at a 
piece of wiie passed at right angles through b, 9 inches 
from it.s point, and soldered to b in that position. This 
wire is about I inch long, and is finished at its ends with 
a shoulder, the object of which will be seen further on ; so 
will the design of the bends in b, above the wire d. The 
wire is of such size that after it is worked down to form 
the shoulder, the round tenon resulting is as large as a 
smiddling size brad- awl. 
I proceed now to the construction. The cross-piece e 
of the compass (Fig. I,) is to be mortised through from 
top to bottom with a mortise inch wide, 3 or 4 inches 
long. Through the centre of this cross-piece, crosswise 
to the mortise, a hole is to be bored with inch centre- 
bit. It is best to bore it before the mortise is made. After 
the mortise is finished, the wood that lies above the bored 
hole must be removed by sawing down from the upper 
edge of the cross-piece two parallel strokes as far apart as 
the diameter of the bored hole. Then provide two pieces 
of brass hooping, about as wide as the cross-piece is thick 
from top to bottom, and of equal length with it (though 
2 inches longer than the mortise will answer.) Through 
tire centre of these pieces drill a hole as large as a com- 
rnon brad-awl. Drill several other holes for small screws, 
making none within two inches of the central hole, guard- 
ing, also, against any of the screw-holes being opposite to 
each other. The central holes are next to be opened out 
to one edge of the pieces by filing with the edge of a flat 
file from the edge of the pieces down to the hole — guard 
against the file’s running suddenly into the hole, and 
tiiereby injuring the roundness of its opposite side. The 
-two brass pieces being thus prepared, screw one of them 
to one side of the cross-pieces, adjusting the central hole 
exactly upon the bored hole in the cross-pieces, with the 
notche from the central hole turned upward, so as to coin- 
cide with the notch from the hole in the cross-piece. After 
securing one brass piece to its place, put on the other on 
the opposite side, and secure it like the former one. Be 
particular to have the central holes opposite to each 
other. 
Next comes the pewter weight, a, and its attachment to 
the index, b. To form it, take a cylindrical block, such 
as merchants receive ribbons on, press the end of an 
inch into earth, sufficiently moist to retain the impression 
made ; then, having melted the pewter, pour it into the 
impression. A better form for the weight would be the 
double convex, as being still less liable to disturbance by 
wind in the direction that might affect its indications. By 
a little management, the weight might be moulded upon 
the index, b. But, if this should not be convenient, they 
are easily connected by running a tenon saw into the 
edge of the pewter weight, in the direction parallel with 
its flat surfaces, as if the intention were to divide it into 
two equal circular pieces. A half inch is deep enough to 
run the saw. Now, slip the wide end of the inde.x into 
the slit made in the weight and solder it there, or secure 
it with two rivets. There must not be any motion be- 
tween them after they are once fixed. The next step is to 
make the hole in the brass piece, b, for the wire, d, (Fig, 
2). It must be drilled at 10 inches from the point. The 
wire to be passed through it must now be laid across the 
two brass pieces on the sides of the cross piece of the 
compass, and just at the notch or slit that runs into the 
central holes. Its ends may there be accurately marktd 
for the shoulders, and then the round tenons must be form- 
ed on them. When the wire has been so prepared that it 
will drop down into the slits and rest, with freedom to 
turn, in the central holes, the shoulders preventing it from 
moving much endwise, it may be taken out and passed 
through the hole prepared for it in b^ allowing it to project 
equally on both sides. In this situation let itbe soldered to 
b. The weight could now be put through the mortise in 
the cross-piece and suspended by the transverse piece in 
the central holes, were it not that the upper end of the in- 
dex, Zi, would be interfered with by the frame of the com- 
pass. To obviate this, the piece h, must be bent twice, 
as seen in Fig. 2. The first bend is just above the wire. 
The second is made far enough from the first to admit of 
the piece being restored, by this second bend, to its form- 
er direction, without striking against the frame. It should 
not be more than ^ of an inch from the first bend, how- 
ever, ns the piece would be reduced too much in length. 
The point o^b is now to be finished off at exactly 9 inches 
from the (centre of the) transverse wire. A thin piece of 
stuff, such as a piece of segar-box, is now to be secured 
to the compass,* so that its upper edge shall be somewhat 
above the point of the index, when the weight has been 
passed down through the mortice, and the ends of the wire 
are in their proper place, in the central holes of the two 
brass pieces on the sides of the cross-piece. Now, with 
a pencil held exactly at the point of the index b, an arc of 
a circle must be described on the thin piece of wood, c. 
At this stage of the work, it will be best to lay by the 
instrument itself, and make a scale on a piece of paper, to 
be transferred, in the manner I shall describe, to the scale 
board, c. The straw-colored paper of which envelopes 
are made, and which can be obtained from booksellers, is 
excellent for work of this sort. It can be got in large 
pieces without folds Provide a piece of this, or some 
other paper, large enough to admit of a circle being des- 
cribed on it by means of a pair of dividers opened to the 
exact distance of 9 inches. In the absence of dividers, 
carrying a pencil, the following is a convenient and cor- 
rect mode of making the desired circle; — Take a piece of 
stout paper (if it has been varnished, or covered with th« 
solution of shellac, all the better) ; cut a strip of it about as 
wide as a finger, and lay down on it a rule or square 
edgewise, so that the length of 9 inches can be accurately 
dotted off on the paper. With the strip of paper still ly- 
ing on a table or board, make a pin hole through each of 
the dots. The holes will be nine inches apart, and you 
will be prepared to make your circle of the size required, 
ft will be much more convenient to have your paper 
listened by the edges to a board or smooth table. Paste 
will answer to fasten it with. Breathe some time upon 
It; and while it is yet as moist as the breath can make it. 
*I would recommend that this piece be covered by pa- 
per secured to it by a solution of shellac in alcohol. And 
vhen the instrument is finished, cover the paper and all 
the scale-board (side and edges) with this same solu- 
tion. 
