[ 716 ] 
found the exact Focus , before I placed the.Microfcope 
on the Tube which receives and conveys the Sun’s 
Rays to the Animal j and, having darkened the Room 
as much as I poffibly could, I had a mod entertaining 
Sight of it on my Paper Screen, at the Diftance of 
Three and Four Feet. The Magnifier P ufed was 
the Fourth in JVilfons Pocket Microfcope. And 
at the Diftance of Six or Seven Feet, but not lb 
diftintd You have in the Paper which accompanies 
this (fee Tab. V. Fig. i.) the exatt Dimenfions of the 
Field of Vifion (as I call it), taken with a black Lead 
Pencil, on the Sheet of Paper which was drained in 
a Frame on purpofe, at the Diftance of about Three 
Feet f from the Focus. You have there the true 
Dimenfions of one of the larger Veflels, not the 
largcft, which, being near the Middle of the Tail, 
appeared but obfeure. And I have added the Di- 
menfions of one, the Screen being removed to Six or 
Seven Feet Diftance. 
In the larger Veflels, the Motion feems to equal 
that of the Stream of Water which is forced out of a 
Veil'd by condcnfed Air; and makes an Appearance 
not altogether unlike it, when the Fountain is placed 
in the Sun : Here you can difeern no Shape or Form 
at all of the Globules, but they lccm all confounded: 
As the Current proceeds, you have beautiful luminous 
Reflexions continually. But in the lefler Veflels, and 
in the Parts moft free from Spots, 1 fever&L times 
law the Globuks of an oblong Form, rdembling 
Emmets Eggs in Shape, which I have endeavoured 
to reprefent in the Paper, gliding along one after 
another, and often at the Diftance* yoU fee them in 
the Figure, fometihies joined tdgether ; but i have 
never 
