Royal Society^ 2oi 
fmaller fi/li whole, and Ibmetimes earth 3 wherefore it is needful 
that it have a power of contracting and ftraitning itfelf, forcibly 
to break to pieces its contents. Their inteftines make feveral 
great windings, a fign the fermentation is but flow therein, which 
is compenfated by the length of the inteflines. The liver has 
much the fame fituation as in other animals, as alio the fpleen ; 
they are provided of a gall-bladder, a 2Juttus CholedochuSy and 
^aricreas^ or rather two little bags faftened to the ventricle for 
the fame ufe^ fi/h have ufually many l^avcreas's^ lb that in 
fome there have been found forty four. They have kidneys, 
bladder, ^c. They have the ovary near the Vertebral of the 
loins • the eggs come out at a paffage below the A>ms^ and the 
male has a like "DuBus, or hole ^ by which they eje^^t their feed 
upon that of the female to impregnate the eggs, rifli are fur- 
nifhed with a bladder on the loins, very large in proportion to 
their bulk, which ferves, by compreffing or dilacing itieh, to ren- 
der the fifh more or lefs heavy, as occaiion requires 3 the fins and 
tail aifiil themlelves in their paffage thro' the water, but it is this 
dilatation that makes them capable of fwimming therein, and if 
this bladder be by any means burft, fo that it cannot be extended, 
the fifh can no longer raife themfelves in the water, but keep con- 
tinually at the bottom. Flat fifh, as foles, have no fuch bladdery 
for they are able, by reafnn of their breadrh, to luflain them- 
lelves in the watery cray-fifli and other ihell-fifli want it likewife 
for the mod part, they creeping only at the bottom of the watery 
and ieveral fifh have them double. 
Mr. Newton'i theory of the Tides esflalfied by Air. Halley. 
Phil. Tranf lSl° 22^. p. 445. 
THE fole principle, upon which Mr. ^rc^'raw proceeds to 
explain molt of the great and furprifing ap|^earances of 
nature, is no other than that of gravity, whereby on the earth all 
bodies have a tendency towards its centre 3 and there is the like 
gravitation towards the centre of the fun, moon, and all the 
planets 3 from this principle, as a neceffary conlequence, follows 
the fpherical figure of the earth and lea, and of all the other ce- 
leflial bodies 3 and tho' the tenacity and firmnefs of the folid 
parts, fupport the inequalities of the land above the level 3 yet 
the fluids, preffing equally, and eafily yielding to each other, 
foon rt-ftore the JEquillbriuw, if dilfurbcd, and ^maintain the 
exa(ft figure of the globe. Now this force of the delcent of bo- 
dies towards the centre, is not in all places alike, but is ftill lefs 
and lefs, as the diftance from the centre encreafts, and this force 
Vol. III. C c de- 
