C 14 ] 
concave Cap over the Globe when it meets the under 
Lid 5 which in full-ey'd People is very confpicuous, 
and well worth obferving. The Manner of the upper 
Lid’s being drawn down is this : 
XXL 
The two fixed Points of the ciliary Edges are a con- 
iiderableWay below, and parallel to, the Equator of 
the Globe of the Eye 5 confequently, when the muf- 
cular Fibres of the upper Lid (which, whilft open, 
form Curves of a certain Dimenfion) contraft them- 
felves, they will endeavour to form ftrait Lines by 
being fhortened : This Tendency to become ftrait 
will force each ciliary Edge over, and beyond, the 
Equator , even to form an inverted Arch below it 5 
for, when once it is forced over the Globe thus far, 
it will naturally pafs a little further, fince the Con- 
vexity diminifhes before it all along, to its utmoft 
Contra&ion. See Tab. L Fig. 4. 
XXII. 
I have been thus willing to explain the Manner of 
the Occlufion of the Eye, which I hope is clear to 
you, Gentlemen 5 jirjl , Becaufe Santorini , in his 
Figure of the Face, makes the Eye-lids meet upon 
the very Equator of the Eye-ball ; and others feem 
to think, that the upper Eye-lid moves not much 
more than the under : And, fecondly> to £hew how 
widely different the muicular Fibres of the Lids are, 
in their Situation and Adlion, from thofe of a 
Sphintter (which is Cowpers Opinion) whofe Office 
is to purfe up any Part round which they are placed, 
as 
