[ 34 *^ ] 
the year, with Its curtate diftance from the earth ; and 
the two firfl; articles of each are the places, which it 
would probably begin to appear in. Thefe will fliew 
in general the courfe of the comet, efpecially at its 
firfl; appearance, which is mod: wanted ; but cannot 
be depended on where its motion is fwift, and may 
be 40^ in a day, the beginning of May, or middle of 
October, From thefe tables, compared with the 
fcheme, I have made another, where the comet 
would begin to be feen any month in the year. 
To conftruft the places, on a large flieet of pafte- 
board, I divided the circumference of a circle ten 
inches radius into degrees, for the magnus orbis. 
On the right point of the ecliptic and focal length I 
drew a parabola like that obferved in 1682, round 
the fun, the center of the circle, and marked every 
fourth day’s motion from the perihelion, and the 
line of its nodes. The co-fme (jf the comet’s incli- 
nation fet off on perpendiculars to this, towards the 
feveral points of the parabola, forms, the projedion 
of it, or points in the plane of the ecliptic, over 
which the comet is at any time perpendicular. 
To find the comet’s place at any time, count how 
long it is before or after its perihelion, and mark the 
place in the projedion of the parabola : lay one edge 
of a parallel-ruler through that point, and the place 
the earth is then in, and the other edge paffing thro’ 
the lun, will cut the magnus orbis at the geocentric 
longitude of the comet : The tangent of the comet’s 
inclination making the perpendicular from the co- 
met’s projeded place to the line of nodes, the ra- 
dius is the tangent of its apparent latitude, making 
the curtate diftance of the comet from the earth the. 
radius. 
