DOI Page / Citation link:
https://doi.org/10.11588/diglit.62828#0101
No. 32, is an Elliplis *, commonly called an oval. This
figure may be confidered, in one view, as produced by the fac-
tion of a cone, by a plane cutting both iides of the cone ob-
liquely to its bafe. In this cafe the elliplis produced muft be
irregular, fince a cone is a folid which terminates to a point at
the top; and therefore any feftion oblique to its bafe muft pro-
duce an oval broader at one end than the other. To demon-
ftrate this, nothing more is requifite than to get a piece of wood
turned in the fhape of a fugar-loaf, and let it be fawn acrofs in
a Hoping direction from the bottom of it, and the furface of
the cut will be an irregular oval. But if a cylinder be cut ob-
lique to its bafe, there will then be produced an Elliplis perfectly
regular, and alike at each end.
It may alfo be obferved both of a circle and an oval, that
they are the only regular fuperficies that are bounded by one
line; and thofe which are bounded by two, are their refpedtive
fegments: as Figures 28, 30, 31, 33, 34.
No. 33, is the Semi-ellipfis, or Half-oval; and it is faid to be
on the tranfverfe diameter, when the right fide is equal to the
* Elliplis, from sXXeKp?, ellipjisy a defeat or omiffion. If a fupernce be apparently round,
but, on meafuring it, if one of its diameters be found lliorter than the other, there is then
a defedt, and we fay that the figure is elliptic.
G 2 longeft
figure may be confidered, in one view, as produced by the fac-
tion of a cone, by a plane cutting both iides of the cone ob-
liquely to its bafe. In this cafe the elliplis produced muft be
irregular, fince a cone is a folid which terminates to a point at
the top; and therefore any feftion oblique to its bafe muft pro-
duce an oval broader at one end than the other. To demon-
ftrate this, nothing more is requifite than to get a piece of wood
turned in the fhape of a fugar-loaf, and let it be fawn acrofs in
a Hoping direction from the bottom of it, and the furface of
the cut will be an irregular oval. But if a cylinder be cut ob-
lique to its bafe, there will then be produced an Elliplis perfectly
regular, and alike at each end.
It may alfo be obferved both of a circle and an oval, that
they are the only regular fuperficies that are bounded by one
line; and thofe which are bounded by two, are their refpedtive
fegments: as Figures 28, 30, 31, 33, 34.
No. 33, is the Semi-ellipfis, or Half-oval; and it is faid to be
on the tranfverfe diameter, when the right fide is equal to the
* Elliplis, from sXXeKp?, ellipjisy a defeat or omiffion. If a fupernce be apparently round,
but, on meafuring it, if one of its diameters be found lliorter than the other, there is then
a defedt, and we fay that the figure is elliptic.
G 2 longeft