Full text: Bacon, Francis: Sylva sylvarum

24. Diſſent of Viſibles and Audibles.

THe Species of Viſibles, ſeem to be Emißions of Beams ſrom the Object ſeen,
almoſt like Odors, ſave that they are more incorporeal; but the Species
of Audibles, ſeem to participate more with Local Motion, like Peroußions or Im-
preßions made upon the Air. So that whereas all Bodies do ſeem to work in
two manners, Either by the Communication of their Natures, or by the Im
preßions and Signatures of their Motions. The Diffuſion of Species Viſible,
ſeemeth to participate more of the ſormer Operation, and the Species Audible
of the latter.



The Species of Audibles ſeem to be carried more maniſeſtly thorow the
Air, than the Species of Viſibles: For (I conceive) that a contrary ſtrong
Wind will not much hinder the fight of Viſibles, as it will do the hearing of



There is one difference above all others, between Viſibles and Audibles,
that is the moſt remarkable; as that whereupon many ſmaller differences
do depend; Namely, that Viſibles (except Lights) are carried in Right Lines,
and Audibles in Arcuate Lines. Hence it cometh to paſs, that Viſibles do
not intermingle and confound one another, as hath been ſaid before, but
Sounds do. Hence it cometh, that the ſolidity of Bodies doth not much
hinder the ſight, ſo that the Bodies be clear, and the Pores in a Right Line,
as in Glaſs, Cryſtal, Diamonds, Water, & c. But a thin Scarf or Handker-
chief, though they be Bodies nothing ſo ſolid, hinder the ſ [?] ight: Whereas
(contrariwiſe) theſe Porous Bodies do not much hinder the Hearing, but
ſolid Bodies do almoſt ſtop it, or at leaſt attenuate it. Hence alſo it
cometh, that to the Reflexion of Viſibles, ſmall Glaſſes ſuffice, but to the
Reverberation of Audibles, are required greater ſpaces, as hath like wiſe been
ſaid before.



Viſibles are ſeen further off, than Sounds are heard; allowing neverthe-
leſs the rate of their bigneſs: For other wiſe, a great Sound will be heard
further off, than a ſmall Body ſeen.



Viſibles require (generally) ſome diſtance between the object, and the
Eye to be better ſeen; whereas in Audibles, the nearer the approach of the
Sound is to the Senſe the better; but in this, there may be a double error. The one, becauſe to Seeing there is required Light, and any thing that touch-
eth the Pupil of the Eye (@ll over) excludeth the Light. For I have heard
of a perſon very credible, (who himſelf was cured of a Cataract in one of
his Eyes) that while the Silver-needle did work upon the ſight of his Eye, to
remove the Film of the Cataract, he never ſaw any thing more clear or per-
fect, than that white Needle: Which (no doubt) was, becauſe the Needle
was leſſer than the Pupil of the Eye, and ſo took not the light from it. The
other error may be, For that the object of Sight doth ſtrike upon the Pupil
of the Eye, directly without any interception; whereas the Cave of the Ear
doth hold off the Sound a little from the Organ: And ſo nevertheleſs th@re [?]
is ſome diſtance required in both.



Viſibles are ſwifter carried to the Senſe, than Audibles; as appeareth in
Thunder and Lightning; Flame, and Report of a Piece; Motion of the
Air, in hewing of Wood. All which have been ſet down heretofore, but
are proper for this Title.



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