C47P] 
2. The Organ and Medium are to be confider'd. And, 
I . The Organ, which is the Ear, is helpt much by placing 
it near 2iWall ( efpecially at one end of an Arch, the 
Sound being begotten at the other ) or near the Surface of 
Water, or of ^Z'^-J^^r^A along which the Sounds are moft 
eafily and naturally convey dj as was before declard. 
And 'tis incredible^ how far a found made upon the Earth 
( by the trampling of a Troop of Horfes, for Example) 
may be heard in a ftill night, if a man laies his Ear dole 
to the ground in a large plane. 
Otacotijiicks here come in for helping the ; which 
may be fo contriv'd (by a right underftanding the Frogref- 
Jion of Sounds ^ which is the principal thing to be known 
for the due regulating all fuch kinds of Inftruments ) as 
that the Sound might enter the Ear without any R'efradiv 
on r but as now they are generally made I refer them to 
Fi^f railed Audition. 
2. As to the Medium, I know not how that, by any 
contrivance of Art, can advantage DireB Hearing, o- 
therwifethen I have declar d already in the propagation 
or conveyance of Sounds^ though to the l{efr ailing or 1^» 
fleiling of them it may very much conduce ^ of which 
prefently. 
And lo lhave done with the firft part of my prefent un- 
dertaking, which is the Comparifon of DireSl Vijion and Ati^ 
dition, as to their Improvements from Art. The reftfoUow. 
Wherefore, 
II. Concerning ^^/Tc^S^r//^)?^;? and it's Comparifon, I 
obferve, that Bjf railed Vifon is always made E% parte 
i. Medij s as l^efleSed is ex parte Qb^e'tit. And therefore 
though Bireil Vifion may be helpYl ex parte ObjeUi, Medii 
\t\Organi; y t J{efraFted can be improv'd only ex par- 
te Medij, ar .. F^eflefled ex parte Corporis oppof/ti alone. 
Unlefsit be ai a mixt or compound Vifion, that is l{e- 
fraSo'l^flext,whQn the refiext raies pais to theEye through 
a refrading Medium, fuch as the Medium Internum, 
G con- 
