MicrROGRAPHIA. 
round Spring (the way of making which trials is obviows enough. }) And 
with he fluid oie or Mercury, Air, Oe, the way of trying which, will 
be fomewhat more difficult ; and therefore I fhall in brief deferibe it. He 
therefore that would try with 4ir, muft firft be provided of a Glafs-pipe, 
made of the fhape of that inthe fifth Figure , whereof the fide A’B, res 
prefents a ftraight Tube of about three foot long, C,reprefents another — 
part of it,which confifts of a round Bubble ; fo ordered,that theréis left a 
paffage or hole at the top, into which may be faftened with cement feveral | 
mall Pipes of determinate cylindrical cavities : as let the hollow OF. ce 
t 
F. i * . of 
G. at , 
H. { sf subs 
I, > be. 2-4. - 5.0f; an inch. 
K. ; 
L. | . | 
M. ; 30 | 
ore ee J tt 
There may be added as many more, asthe Experimenter fhall think fit, 
with holes continually decreafing by known quantities, fo far as his fenfes 
are able to help him ; I fay, fofar, becaufe there may be'made Pipes fo _ 
{mall that it will be impoflible to perceive the perforation with ones -na- 
ked eye,though by the help of a A@crofcope, it may eafily enough be per- 
ceived: Nay, I have made a Pipe perforated from end to end) fofmall, 
that with my naked eye I could very hardly fee the body of it, infomuch 
that I have been ableto knitit up intoa knot without breaking: And 
more accurately examining one with my Aficrofcope, Ifound it not fo big 
asa fixteenth part of one of the fmaller hairs of my head which was of 
the {maller and finer fort of hair, fo that frxteen of thefe Pipes bound fag= 
got-wile together, would but have equalized one fingle hair 3 how fmall 
therefore mutt its perforation be? It appearing to me through the Aficro- 
Scope to bea proportionably thick-fided Pipe. i 
To proceed then, for the trial of the Experiment, the Experimente 
mutt place the Tze A B, perpendicular, and fill the PipeF (cemented in- 
to thehole E_) with water, but leave the bxbb/e C full of 4ir,andthen 
gently pouring in water into the Pipe A B, he muft obferve diligently 
how high the water will rifein it beforeit protrude the bubble of AirC, — 
through the narrow paflage of F, and denote exaély the height of the — 
Cylinder of water, then cementing in afecond PipeasG, and filling it — 
with water 5 he may proceed as withthe former, denoting likewifethe _ 
height of the Cylinder of water, able to protrude the bubble C mati 4 
the paffage of G, the like may he do with the next Pipe,and the next,O7. 
as far ashe isable: then comparing the feveral heights of the Cylinders, 
with the feveral holes through which each Cylinder did force the air(ha- 
ving due regard tothe Cylinders of water in the {mall Tubes) jt willbe 
very eafie to determine, what force is requifite to prefs the Air in- 
to fuch and fuch 4 hole, or (to apply it to our prefent ee I4 
Lt : ow 
