( ^HS ) 
of the Brafs Plate, faftiied to the Cork F, under the other 
two thin Plats of Brafs EE : When the Tail of your 
Fifh lyes flat to the Glafs Tube, fet it oppofite to your 
Magnifying glafs, and by fcrewing in or out your End 
Screw D, as is faid before, you may eafily bring it to the 
true diftance, and fee the Blood circulate with great plea- 
fure. 
. When the Bigger Tube is to be ufed with a larger Fiffi^ 
or Frog 3 then you are to take out the Brafs Plate G F 
faftned to the Cork, by preffing dovyn the other two Plates 
EE and the Spring H to the end of the Microfcope B3 and 
by turning the Cork and Brafs Plate G F fideways, you 
may eafily either take it out and put it in again 3 when the 
Cork-plate G F is out, the larger Tube will eafily enter in- 
to the body of the Inftrument, and is to be ufed as tha 
other lefTer one. 
If you v/ould fee the Blood Qrmlate in a Frogs Foot, 
choofe fuch a Frog as will juft go into your Tube, then 
with a little Stick, &c. expand the Hinder foot the Frog, 
and apply it clofe to the fide of the Tube, obferviog that 
no part of the Frog hinders the Light coitiing on its 
Foot, and when you have it at the juft diftance, by means 
of the Screw D,. as abovefaid, you will fee the rapid Moti-' 
on of the Blood, in its Veffels, which are very Numerous, 
in the Tranfparent thin Membrane that's between the Frogs . 
"Toes : For this Objeft the 3d and 4th Magnifyers v/ill do . 
very wtH 5 but you may fee the Circulation in the Tails of 
V/atcr-Ntwts with the. 5th and 6th Glafs, by reafon the 
Globules of the Blood of thofe Newts are as hm a^ain as 
the Globules of the Blood of Frogs of fmall Filh. v a3 has 
. been taken notice of by Mr G.rf7j?ejr! in N. 280.- of thefb 
Tranfaftions, pag.^ 1184. . 
B. The CtrcuUiion cannot be fo well feen by the ift' 
and, 2d Magnifyers, becaufe the thicknefs of the Glafs 
wJiereia the FifliJ yes hinders the Approx. . 
