on a ‘Planet Mars. * a 
1783, Nov. 11. The deficiency of light which occafions Mars 
to appear gibbous, reaches over the fouth polar {pot 
| towards the preceding limb, and hides it. 
e Nov. 14. Mars. is gibbous, and the polar {pot is thereby 
rendered invifible, | 
Nov. 17. 6h.0’. The fouth polar fpot is under the fal~ 
cated defe& of light. 
6h. 30’. I do not know whether there be not a faint 
glimpfe of the polar fpot left; the weather is too 
bad to determine it. : 
I have added fig. 25. (tab. X.) to fhew the conneétion of the 
rsth, 17th, 18th, 19th, 20th, a1ft, and 22d figures, which 
complete the whole equatorial circle of appearances on Mars, 
as they were obferved in immediate fucceffion.. The center of 
the circle marked 17 is placed on the circumference of the 
inner circle, by making its diftance from the center of the 
circle, marked 15, anfwer to the interval of time between the 
two obfervations, properly calculated and reduced to fidereal 
meafure. The fame has been done with regard to the circles 
marked 18, 19, &c. And it will be found, by placing any 
one of thefe conneéted circles, fo as to have its contents in a 
fimilar fitudtion with the figures in the fingle reprefentation 
which bears the fame number, that there is a fufficient refem- 
blance between them; but fome allowance muft undoubtedly 
be made for the unavoidable diftortions occafioned by this kind 
of projection. | 
In order to bring thefe obfervations on the bright fpots into 
one view, I have placed them at the circumference of three 
circles (fee fig. 26, 27, 28. tab. VII. VIL. IX.) divided into de- 
grees, reprefenting the parallels of declination in which they 
wow. LXXIV; Kk revolved 
