SOUTHERN CULTIVATOR. 
311 
wire that passes through it) the same will exist between 
the divisions of the scale and a standard inch. Thus, a 
9 inches index and inch scale on a 12 feet or 144 inches 
rafter, will show, for every division of the scale 4 inches 
elevation or depression of one foot of the rafter equal, 
therefore, to 4 inches in 12 feet; for 144 inches divided by 
9—16. But as the scale is not in inches, but in fourths 
of inches, so the 16 is 16-4—4 inches. And this corres- 
ponds with the indications of the same instrument when 
attached to a 3 feet compass ; 1 inch elevation or depres- 
sion for every 3 feet, which is 4 inches for every 12 feet. 
Let me, then, in concluding the descriptive part of this 
article, suggest a modification of the above instrument, 
whereby it may be rendered convenient of attachment to 
any kind of frame. 
Provide a piece of well dressed and seasoned plank 
about % of an inch thick and 10 inches wide. Take a 
point at midway between the two ends and half an inch 
from one edge, and upon this point, as a centre, describe a 
circle with a radius of 4 inches or a little more. Cut the 
circle so formed, and your piece will then have a semicir- 
cular hollow in one edge. Now secure two such pieces 
of brass hooping, as were fastened to the cross-piece of 
the compass, on the edge of your board hollowed out, (one 
piece on each side). They will extend across the semi- 
circular hollow, and will face each other. The central 
holes must be opposite to each other, and should be about 
halfway accross the hollow. The weight and index can 
then be suspended as upon the compass, and a circle 
drawn and graduated as already described. A few holes 
for screws will make it ready for attachment. After des- 
cribing the circle by means of the index, it would be well 
to cut away the excess of wood for about of an inch be- 
yond the circle, and to make the 0 point on the arc of the 
circle about midway between the extremeties of the arc. 
And now, as this point is supposed to be fixed upon, 
some address is requisite in attaching the instruments to 
a rafter, so that when it is level the index may be at 0. 
For this purpose, secure the instrument by one screw 
only, as nearly in its right pssition as the judgment will 
enable you to do — the rafter being on a floor and held in 
a working position. Mark on the floor, with a pencil, 
around both feet of the rafter. Witliout disturbing the ar- 
rangement, observe where the index is, and make a fine 
, pencil-mark on the circle. (The divisions of the circle 
m-wst not be used). Now turn the rafter, and put each foot 
where the other stood. Without disturbing the arrange- 
ment, observe and mark again the place indicated by the 
index. If it should not be exactly the same as the other, 
find the middle between the two indications and mark it 
with a fine pencil. This is the point at which your index 
will stand if you now place your rafter on a level. But 
you require your index to be at O when your rafter is 
level, or none of its indications on the scale will be cor- 
rect. We will now adjust this matter. If your rafter, 
by mere accident, is on a level at the place where you set 
at; your index will point to the same place after reversing 
the feet of the rafter, that it pointed to before reversing 
them; and you will not have to make a second and third 
mark ; you can then also keep your rafter in this place 
until you have done the work, which in this position, is 
nothing more than turning your instrument upon its one 
screw until 0 comes to the point of your index, and then 
securing it by the other screws. If, however, your rafter 
was not level, and consequently you had to make a 
second mark, and then a third between the first and second ; 
then you must have a wedge slipped under the lower foot, 
until the third or middle mark comes to the point of the 
index. Now hold the level in this position, and turn yowr 
instrument on its screw until 0 comes to the point of the 
index ; and then secure the instrument in this position 
with the other screws. The rafter is now ready for use. 
Every division on the scale is equivalent to 4 inches; for 
as the 9 inches radius is equal to the 1-16 of the 144 
inches radius, so 1-16 of an inch on the scale would be 
equivalent to 1 standard inch. But your divisions, being 
fourths instead of sixteenths, are of four times the value, 
hence, instead of being equivalent to 1 inch, they are 
equivalent to 4 inches. 
For the satisfaction of those persons who may not be 
disposed to examine the reasoning in this article, I will 
state that my comapass level has actually worked most 
successfully in every kind of grading that is done on a 
farm. And, for sake of proof, I attached the compass, 
with the instrument on it, to a 12 feet rafter with spirit 
level, and tested, by actual experiment, its indications 
with known elevations of 1 foot of the rafter, and found 
them to correspond most accurately. 
My instrument is the work of my own hands, with no 
other knowledge of the use of tools, than I have acquired 
by indulging a natural fondness for using them. I believe 
that a mechanic would find it profitable to make, for sale, 
so much of the instrument as may be attached -to a rafter 
or compass, marking on each the value of the divisions of 
the scale to a given stride. And from this their value to 
any other stride could easily be found. For example, sup- 
pose the instrument to be marked 1 inch to 36 inch stride, 
meaning that on a compass of 3 feet, or 36 inches stride, 
the divisions of the scale are equivalent to 1 inch; then, to 
ascertain their value on a rafter of 12 feet, or 144 inches, 
make the statement 36 inches stride to 144 inches, as 1 
inch val. to 4 inch val. 
The advantages of this Level are more than I can point 
out at the end of this long article. I would briefiy say, 
however, that, unlike the spirit level, it shows the 
amount of elevation or depression, and therefore can be 
used for any grade, varying it at pleasure, without any 
re-adjustment. And if, injrunning horizontal furrows, or 
hill-side drains, a stump or tree, or hole not sufficient to 
warrant a change in the direction, should come in the 
way of the foot of the instrument, it may be placed on 
either side of the obstacle, and the index will show how 
much too high or too low it is; and at the next step a com- 
pensation is easily made if there was loss, or, if there was 
gain, as much may be deducted ; and this, too, without 
the least detention. This may be done with the plumb 
and line level, provided it has a scale. But unfortunately 
if it has, it must necessarily be so low down, to be very in- 
convenient to observe ; and it is liable also to be interfered 
with by bushes. The plumb-line is also liable to dis- 
turbance by wind, and is altogether an awkward thing, 
for you cannot help it much in settling. But you can 
make my level settle by a touch of the finger, easily made, 
as it is raised to a convenient height. Another advan- 
tage over the spirit level is, that, by means of mine, you 
can decide, between several points, which is the highest, 
or lowest, and what the difference is. In this way, you 
may ascertain what direction flowing water will takei 
Now, with the spirit level we can find that a point, as A, 
is lower than B, but to know whether B is higher or low- 
er than the rest of the surrounding surface, the entire 
level must be lifted and its feet so placed that a compari- 
son may be made between B and the surrounding surface. 
And then when you have thus found that C is Jiigher than 
B, you do not know whether it is as high as A. But sup- 
pose my level to be used — one foot may be kept on A, 
while the other is carried around a full circle, and the 
relative heights of all the points touched may be read of 
from the scale. The lowest is fixed on as the course of 
running water going from A. I have found great practical 
advantage in this peculiarity of my instrument. But, like 
others, they are more readily appreciated in practice than 
in reading any description of the instrument or its appli- 
cation. Wm. Johnson. 
Glenwoodj Tuscaloosa, Co.^ Ala.^ August^ 1855, 
