Objections of M. de la lande. j 
It is mob true, that if we look for any thing like this, when 
the plane which coincides with the external boundary of the 
Ipot paflcs through the eve (the way that M. DE la lande 
conliders the matter, vide his fig. 9th) it mud be very large 
indeed before the ddk could be perceived deficient bv any dark 
fegment. But may not a fpot, even no- larger than M. Cas- 
sini’s, conlidered as an excavation, make, in a manner very dif- 
ferent from this-, fomething like a notch ; for, by the way, this 
phenomenon is not in. the Mem. Acad, nor any where die, that 
1 know of, deferibed with any fort of precition. 
M. Cassini’s great fpot, by which we under flood the nu- 
cleus, was one of 30'' ; and fuppofing the umbra equally 
broad, its diameter over all mufl have been 1' 30 It would, 
therefore, occupy an extent upon the fun’s furface of 5 0 22 ' 
fully. Now, fuppofc a circular fpace of that fize upon the 
fun, diflinguifhed from the furrounding luftre by fuch a failure 
of light as is peculiar to fome fpots, and fuppofe that it juft 
touches the limb, it would dill fubtend an angle of more than 4". 
This being the cafe* might not a dufky fhade, more or lefs 
remarkable, according to the darknefs of the umbra, com- 
mencing at the limb, and reaching inwards upon the difk, or, 
in other words, a notch, be perceived ? Had M. Cassini’s Ipot 
been a very /hallow excavation, it appears by cafe fourth, for- 
merly dated,, that when viewed in this afpefl, fome final! part 
of the nucleus might have been yet vifible, and might have 
contributed along with the fhade of the farthefl umbra, and 
the dill deeper and broader fhade of the two ends of the umbra, 
to mark out the indentation. 
Should it be laid, that thefe notches are always dibincf jet 
black imprefdons on the dilk, of an obvious breadth, and ori- 
ginating entirely from the opaque nucleus conceived as fome- 
thing 
