E X P L A N A T I O N or THE TABLES;
diameter of the fphere A B C D , and its thicknefs or length of its axis equal to
the radius of the fphere,
^rfand /JA, The radii by which the fedion of this lens was deferihed.
3. The focus of parallel rays, after palling through fuch a lens filled with
water.
Hence tlie focus of fuch a lens is nearer to the fore part of it than the focus
of the fphere is to'its fore part by the length 3 F ; and the focus D of the lens
A b d e i s only a diameter of the fphere A B C D diftant from its fore part:
whereas the focus of the fphere itfelf is diftant from its fore part A a diameter
and a half
t a b l e XLL
IN this and in^ the next Tabic, the ftruclure of the Sepia Loligo is reprefented.
A A, The tail of a triangular fliape.
B B, A hollow mufculir flicath, which inciofes the body, cut open.
C, A flclliy funnel, with its conical point turned forwards.
D D D, &c. Ten ilelliy arms furrounding its mouth.
E, A few cups painted, of wliich there are many on each arm.
r . The mouth, which has a beak refembling that of a parrot.
G, Part of the cefophagus.
H, The ftomach.
I, Part of the upper end of the internal canal.
KK, The reélum and anus.
LL, A duller of glandular-like bodies, which probably is the ovarium.
MM, A very large liver.
N, The ink-bag.
G g O,
1,1 Cl»p,cr ¡a. I .llcgcJ Ih., He „«s of He Iris i„ m„, ,„<1 ,„,J„,,d. „ „„, „ d. Perni,, ,„d
Dr H>lkT n„sl,i, b«. conve, red blood. I„ full conSrm.li.n ot whid,, I ,veuld here >dd, ihtt i„ tl,e irà of ,l,e
I,„„g^wh,te nbbil, where dio pign.eni i, w.mioj „ well is ¡o ibeir ehoroid coat, I l,„e fee„ witl, ,he n.tod e,e, .nd
II,11 more d,lh,>aiy vvlth niagolfyiog ghfs, oumcrous veiTela full of red blood.
If im.ll feon „eceir,,, ,„ l,„o «ili ele.re, proof tbin w. gi.en io CI,. M. of ll,e toce«r.c, of Dr Petiis T.ble, oí
ll,e breiddi, rhiekocS, and r.dii of ihe bom», crjlhllioe leoj, j, „eli a, ot ll.ji of tl,e o,, I .-ould obferve, Tha the
b,e.d.h i„d rhictaefs of N- S. , 3. , , S. a,. of >l,a Table .,ro fiid .0 be tire f™e , ,el boti, r.dii of N- „ . aro repre-
Ceoled .a greatl, looger tl,an ll.of, of ,l,e otlter number,. Io like manuer, boti, «dii óf N» ,. „e louger that, ¡o No j.
a„d the radius of the autcrior com.exit;i of tire le,ls i„ 1. is longer than that of N' .3. , 7. 18 ; while the radius of the
pofterior eonvexit;^ is the fame in all thefe. But it is demo.,Arable, and indeed at firlt fight evident, that if the breadth
of Icnfes, compofed of portions of diflerent fpheres, bo the fame, tlieir thicknefs mud vary aecording to the radii of thofe
fplicrea.