OVA 
done, the moft perfe& workmanfhip in the grooves and 
| can aba enfure that it fhall move freely without 
‘eae mproper motions, fo as to ma ke an accurate and 
fair 
All ice defects are eaghani es in the abe invention, by 
extending ‘the two point o become the large cir- 
cls A, B, fig. 33 then if e alee D, E, ' G, reprefent 
the fides of the grooves in whic oints move: the 
of along the 
diminith the elli fe, but with the advantage that it can be 
actually brought to coincide with one of the points d or e, 
when of courfe it will draw a ftraight line, and if brought to 
match with b of them, it will defcribe only a point 
therefore this inftrument will defcribe any poffible variety 
ellipfe within the limits of its radius, either as to fize or pro- 
portion of its diameters 
In the ufe of this inftrument, when any ellipfis of given 
dimenfions is to be drawn, the paper is prepared by drawing 
the two diameters about four inches long ; upon each of 
thefe fet off, with the compaffes, the four points steal 
the intended curve is to interfe& the lines. 
fitting, the se ea is ready for ufe; turn the circles 
os in the frame, to bring the pen towards the fide marked 
ew place the whole inftrument in {uch a pofition, that 
the mate of the four rulers coincides with the centre of 
the intended ellinfis. This may be eftimated, or, by pre- 
vioufly producing the two diameters, the frame may be fet 
ie A nearly, taking care to place the upper rulers F, G, 
: here fix th 
oe thumb to any oot two wi = {mall bee va of 
pen 
ee dee 
of a elit ; then turn the circles one-half round by the 
handles, and examine if the point of the pen comes exadlly 
to the oppofite mark for the end of the fhorteft diameter ; 
if it does not, adjuft the. error, aie lf by moving the 
pen, by turning the pinion L, and the other half, by moving 
the whole frame on the paper. The fcrews of the nuts 
N, O, will admit this motion, being fitted into grooves in 
the ruler P, (which fhould not be Fifturbed, ) but the nuts 
me fideways on the ‘paper. T'o do this, she ate nuts 
N,0O, oa be made flack, and then the frame will be at 
OUA 
P muft never be removed’ 
of the frame will, of 
The adj 
liberty:to move; but the ruler 
after the firft fixing, and the fide 
courfe, be at a ia or = diftance from it. 
noes nner, t 
e pape per r the 
preeiuibas OF turning ie circles to ae oppofite foe vil 
be unneceflary, except where great accuracy is requi 
In turning the ee about, a habit will be acqui met “of 
prefling with equal force on the two onrpofite fides of the 
—— and then they will turn round eafily. 
will fave much trouble, in adjufting the place of the 
henaent upon the Papers : the compaffes, before being 
put into the focket H, yee ned to the extent of the 
two marks upon the bar G; hen t 
into their focket, and if this is removed by turning the 
pinion, L, tiil the end, &) comes in conta with the es of 
the circle, the point of the en 
After having drawn an ellipfis, if it is required to draw 
another pe to it, to fhew the thic nets of a circular 
plate, for inftance, fet the pen oppofite G, and ib the 
» a8 before mentioned, being fitted 
in grooves, t and the cireles may be moved with 
the longer axis paral to itfelf, fo as to defcribe another 
ellipfis parallel to By this means all kinds of 
circular mou ne w els, &c. may be drawn with the 
greateft accuracy and expedition; but is various ufes to 
which it is applicable, are beft fhewn by the numerous 
perf{peGtive drawings in our plates, ere Mr. Farey em- 
ploys it fo: all the ellipfes 
oN olumn. See CoLumn. 
nts have been reprefented as authorifing this 
deformed Goi or the plan of a colum u is a 
iftake, probably occafioned by the dicen of fragments, 
where flanked c ns have been fet back to back a a 
umns: thefe r time, might fuggett, 
7 a fiperacal pai that the leat originally had an 
al bafe. 
re Cr See Cro 
Ovat Ell; spf, an bine cnvlnes figure with two un- 
clofed with a fingle curve 
eing pal than its 
e OVAL. 
points or nails, F, f, P lante 
which means the oval is made 
two points or nails are farther a 
VAL Foramen, Pic aalae in 0 Surgery See Hernia. 
Lea 
OvAL ak in Botany. See 
OUA DE, in Geography, a ua of Africa, in the 
country ee the Foulahs, on the fide of the Senegal. N. 
Jat. 18° 45/. ng. 13° 
OVAL FoRAMEN, in ye 
Vv tomy 
OVALLE, Atoyzo it: in 5 ge a "Telit was 
