I to t : 
view, and I faw it diftin&Iy, though narrower than ' 
the other fides. After this, my obfervations were 
interrupted, by unfavourable weather, till the 1 7th* 
when the fpot had pafled the center of the difc, the 
umbra now appearing to furround the nucleus 
equally. . Fig, 3, 4, aud 5, reprefent the-fpot, as it 
appeared on December 1 ith, 1 2th, and 1 7th, when 
it came upon, the. difc for. the fecond time.. 
All the foregoing. appearances, .when taken to- 
gether, and when duly confidered, feem to prove 
in the moft convincing manner, that the nucleus 
of this fpot was confiderably beneath the level of 
the fun’s fpherical furface. 
The, next thing, which! took into confederation^ 
was to think of fome means, whereby I could form 
an eftimate of , its depth. At the time of the ob- 
fervation I had on December 1 2th, I had remarked, 
that the breadth of the fide of the. umbra, next the 
limb, was about 14" ; but, for determining the 
point in queftion, it.was alfo requifite, to know the 
inclination of.theihelving fide of the umbra to the 
fun’s fpherical furface. And here it occurred, that, 
in the cafe of aiarge fpot, this would, in fome mea- 
jfure, be deduced from ohfervation. For,, at the time 
when the.vfide of the umbra is juft hid, or begins - 
fir ft to come in view, it is evident, that a line join? 
ing the eye and, its. obferved edge,, or uppermoft t 
limit, .coincides with the plane .of its declivity. . 
By meafuring. therefore .the diftance of the .edge 
from the limb* when this change takes place* and 
by reprefenting . it by a projection, the inclination ■. 
or, declivity in, fome meafure may be afeertained, 
For in fig. 5. [Tab.. II.] let IL D K be a portion 
1 r oft 
