i 'o Dr. wilson’s Anfwer to the 
meafures; though very unequal in the third dimenfion HE or 
depth ot : the nucleus 5 L, and alfo in the inclination DGM of 
their (ides to the fpherical furface of the fun. Now it is ma- 
in fell:, from the conftruCVion of the figure, that the diflan ces 
AB, AK, from the limb A, when the tides GS of the umbra 
difappear, muft depend very much upon the laft of thefe two 
circumftances ; and that, according as the angle cf inclination 
DGM islefs, the refpe&ive fpot will go nearer to the limb than 
the other before the tide of the umbra GS vanifhes. But 
thofe very exceptions to the general phenomena which we are 
at prefent examining are of this kind, and may, perhaps, from 
what has been now {hewn* proceed wholly from the fhallow- 
nefs and the very gradual (helving of fome few fpots which 
break out in certain tracts of the fun’s body over which the 
luminous matter lies very thinly mantled. 
If, .therefore, upon fuch principles it can be fhewn, that 
fpots, fimilar to the reft, may fometimes go to the limb with- 
out the one umbra contracting fenfibly more than the other, the 
objection we are at prefent confidering will be entirely removed, 
and it will be allowable to conclude, that even thefe few fpots 
are excavations like all the reft, though fhallower, as it would 
be quite unphilofophical to multiply diftinCtions concerning 
their nature, where there is found no neceflity for fo doing. 
In order to avoid circumlocution, we may call that fide of 
.the umbra which lies : neareft the limb the near eft umbra, and 
the fide oppofite the fartheft umbra\ and to enter more particu- 
larly into the confideration now before us, let us fuppofe a fpot 
of 40" over all, with its nucleus and umbra equally broad; 
then will the depth of the nucleus and the apparent breadth 
of the neareft umbra, when the plane-of the fartheft comes to 
coincide with the vifual ray, be as exprefted in the following 
examples, 
