789 



PLATE XXXir. 



rig. 471. A representing the sun, B tlie eartli, and 

 C the planet Mars; supposing Mai's and the earth lo 

 net out to;;et!ier from D and E, the angle D A C was 

 letermined by Kepler from calculation, and the angles 

 BAD and ABC hy observation ; whence it was easy 

 to construct the triangle ABC, and to find the pro- 

 portion of A B to A C. P. .505. 



Fig. 472. The solar system, representing the form 

 and proportions of the orbits of all the primary planets, 

 and of three of the comets. The parts of the orbits 

 represented by entire lines are on the north of the 

 ecliptic, the dotted parts on the south : the letters A 

 nnd P denote the aphelion and perihelion. The point 

 in the centre, which ought to be only 7J5 of an inch in 

 diameter, represents the sun. The figures of the re- 

 «pective planets show their comparative magnitude, 

 that of the sun being represented by the innermost of 

 the graduated circles which inclose the whole : they 



are placed according to their actual situations on the 

 14th June, 1806. The letters M D show the mean 

 distance of the comet of 1759, being placed at the ex- 

 tremity of the lesser axis of the ellipsis in which it 

 must be supposed to revoWe. P. 514. 



Fig. 473. The periodical times of the different pla- 

 nets, represented by lines of different lengths. P. 

 514. 



Fig. 474. The comparative velocities of the dif- 

 ferent planets, represented by lines which show the 

 number of English miles described in a second, on tht 

 scale marked on the lowest line. P. 514. 



Fig. 475. The places of the ascending nodes of all 

 the planets, marked on one half of the ecliptic, sup- 

 posed to be extended in a straight line ; together with 

 the inclinations of their orbits. The line marked 

 F. F. £. £, shows the situatioQ of the fixed ecliptic. P. 

 514. 



VOL. I. 



5 F 



