Thus much I have thought proper to premise, and for your immediate Inspection, have added the following Schemes, that nothing may be wanting to give a general Idea of the Order of the celestial Bodies in our own System, before I attempt to lead you through the neighbouring Regions of the Stars to the more remote Tracts of Infinity.
PLATE IV.
Is a true Delineation of the solar System, with the Trajectories of three of the principal Comets, whose Periods and Orbits have been accurately determined, and are represented in their true Proportion and Position to one another, and the Order of the Planets round the Sun, marked with their respective Characters, viz. ♄, for Saturn, ♃, Jupiter, ♂, Mars, ♁, the Earth, ♀, Venus, and ☿, Mercury. The Scale being nearly five hundred and eighteen Millions of Miles to an Inch.
PLATE V.
Is a true Projection of the System of the known Comets; in which are represented nine of the chief Trajectories, from their Aphelii to their Perihelii, all in just Proportion and Position to the Orbits of Saturn and Jupiter, which are also represented by the two concentric Circles, supposed to be drawn round the Sun as their Center.
The Ellipsis, or Trajectory, marked A, shews the Position and Path of the Comet which appeared in the Year 1684, whose Period is supposed to be about fifty Years, and has been observed within the Region of the Planets once.
That mark'd B, is the Way of the Comet of 1682;
The Period conjectured to be about seventy-five
Years and a half, and has been observed thrice.
C, Way of the Comet of 1337;
The Period about 100 Years, observed once.
D, That of the Comet of 1661;
The Period about 129 Years, observed twice.
E, Tract of the Comet of 1618;
The Period about 160 Years, observed once.
F, Way of the Comet of 1677;
The Period about 200 Years, observed once.
G, Way of the Comet of 1744;
The Period about 300 Years, observed once.
H, Way of the Comet of 1665;
The Period about 400 Years, observed once.
I, Way of the Comet of 1680;
The Period about 575 Years, observed thrice.
Plate IV.
Plate V.