The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1856-08-22

ef between the wall and the wood the loudrsss OF the
echo Of single use would te increased white tho du
ration of the echo would be diminished. II, however
the thin board glued oemeEted ~ sosu oenuec
tion 10 the wall embedded IN The motar .aeA Toe Oh
feet would be feeble echo, and iong cohtnasi reso
pancc similar 10 that from tho sisb Of marble Fhs was
proved by first determining the length Of continuance "
The vibrations Of tuning fork on thin bora Wh'cn
was after wards cemented To tat piece OF ma ole
A series Of experiments wevu next commenced VIA
reference tire actual rehect5o OF sound fof Ivy par
pose parabokc mrrcr was empoyeu, aea .aa soua s
HON watch received or -ne mouth OF hssrng uuin
pet furnished with tube vor each ear inc locus was
near apex Of The peEuoola and when me wasn wa
suspended al this pc six inches within tue p'sne
OF the outer circle q In this case The sound
was confined at It's origin aud prevented from expanding
No ocpugate focsss produced but on the contrary
the rays Of light when candle vas introduced constant
~ diverged The ticking OF the watch could na. DO
heard at all when the applied 70 the OUTSIDE OF
The mirror while directly front distinctly heard
the distance of thirty feet and with the assistance Of
When na he watch was removed nom the focus the souad
ceased be audible. This method of experimenting
admits Of considerable precision, and enables as V
through air, the results anticipated the previous
permsn ecs 81 tissue s PAPER v yassa o s ~
slightly diminished the reflection simple curtain On
flannel produced somewhat greater enec though me
rejecting power Of the metsc parsooa was nG' enur.y
masked by three thicknesses of flannel and presume
very little change would have been perceived had TIE
reflector been hnef with flannel glued 70 the surface OF
The metal The sound also audible at the distance OF
ten ieet, when a large felt hat without slhen,ns, was
ierposed between the watch and The mirror Care was
taken IN experiments to surround the watch that
ray Of sound could pass directly from J, TO tho Reject
with a cylindrical mirror with parabolc base very
little rehe tion perceived The oonye gng
were merely Ins s ws
tohe focal point Of the spherical mirror sohd cone o.
The reelection from The cylindrical mirror forms what
Is called caus.ic in optics, while that from spherl
cal mirror gives true focus, or, n other w9as
and conveys them to one point OF space. These
facts furnish ready e1pia az o. M me
which is surmounted by DOME the under surface OF
WIN CHI acts as an concave mirror rejecting 70
focus every sound which ascends TO 1t, leaving otner
points OF space dc fcent In sonorous impulses.
Water other liquids which offer great RESISTANCE q
compression good refectors OF sound THIS may be
shown by the following experiment:-When water 5
gradually poured into upright cylindrical veseei over
comes within a certain distance OF the mouth viii re-
fest echo in unison with the vibrations OF the iosx
and produce loud resonance 1s reSa ss
the duration Of the Of newly pastered room
percepby less than that Of one which lad been
There IS another principle Of acoustics which has
bearing this subject. alnde to the refracton o.
tound. II is well known that when aray OF sound passes
from medium to another change in velocity takes
place. and sequenty change in the direction or re-
fraction must produced. The amount OF this readi
IL be calculate the relative veloce, FLOWN.
In heated by furnaces, AMI in which streams Of
on has been Supposed to be iaced and nct
hearing nterfered with by this cause Since INC veioc
found 10 be $50 second and since the yeooty
increases IA feey for every degree Of Fahrenheit We
know the temperature Of the room and that Of tbe beat
the amount OF refracton can DC aSc3r
tanned. But since the does not readily Judge " tue
difference OF direction of two sounds enanatng iron the
same source and rays do not confuse the IN
arrive by very routes provided they within
that the ndisnciness produced by reraton Is compare
lively little. Professor Bacbe and myself could perceive
no difference in dstnctness In hearing from rays OF
sound passing chandelier OF the largest sire, in
which large number Of gas Jets were in fui oonouston
The fact OF dsurbarc from this cause, however fany
EXIT may best be determined by the experiment wi.h
parabohc mirror and the hearing trumpet before dos
cribed.
These researches may be much exten ed; hes open
field CT investigation equally interesting 70 the lover Of
abstract science and to the practical builder And hoe
behalf Of the committee, To give some further facts
with regard 10 this subject At another meeting.
will now briehs describe the lecture room which has
been with the facts prnci
pies stated above, so lar, al least as THEY could be ap
Piled
There wns another object KEEP, n view in The con
sruc,on OF this room-besdes hearing, the
| lssipct seeing. II was desirable that every person
should have opportunity Of seeing the oerments
which light be performed as well as hear distinctly
explanation Of them.
by fortunate coincidence Of principles, Il ha opens
that The arrangements for ensurng nobstucted sight do
ct interfere with those necessary for distinct hearing
The Smithsonian inst,ut ON directed that lecture room
should be provided and accordingly IN the trst plan
me ban o. the frat story Of the ma building WAS lie
possible 10 construct room on acoustic prin-
tpes in this part Of the bosdng which WAS necsssa
bic place which could be fcGnd the.eGse cn the
second foor The main building 900 eet ior ard 50
feet wide but by placing The lecture room the middle OF
the story greater width obtained By Of the
projecting towers The general form and arrange nsnt
Of the room will be understood from the accompanying
drawing (Herc the speaker referred 70 drawing and
explained ~
The gallery in the form Of bor,e shoe ana oc-
cupes three sidce Of The The speakers platform
placed between two oblque walls The corIe-s Of the
room which are cut on BY these walls AFFORD rec ,es for
also parttoncd OF 60 10 afford recesses for the
purpose
The reach Of perceptbity. II perfectly smooth an
urbrosen with the exception Of an oval operng nesr me
platform through which Ugh; Is admitted
he seat ranged in curved form, and we're IL
tended 10 rEe accordance with the psnortac .rrve
originally proposed by Professor Blshe, Which enshos
every individual head OF the perscs
medatey in front Of him, The original form Of the ROM
however I'D not allow Of this intention being fully s,i,sd
and therefore the Is somewhat less than the curve
would indicate The general appearance OF tho room V
somewhat fan shaped and the Speaker y placed ~ i
In the mouth or inmenge q umpet. TIE sound
directly from bis voice, and that from reaccto, mme
| dstely behind him, IL thrown forward upon TIE ~
depcc, ard e difference Of the d. lance travelled by
the two rays s much within the limit OF Icrcepbi y
confusion produced BY direct and reflected soaai
No echo is Given OF from the ceiling, cr this q also
within the limit Of pcrccpsbity, while i assst,
hearug in the gallery by tho reflection % thai place Of
Again, on account Of the oblique walls behind The
speaker and the multitude Of surfaces including The gal
cTy pillars, stair screens &c, vel as the audience,
directly In front all reverberation IS stopped.
The walls behind the speaker are composed 81 'ath
aud plaster and therefore have tendency 20 gsea
intense though less prolonged sound than 81 solid
masonry They also intended Cor exhibiting drawings
10 the best advantage.
The architecture Of this u due 10 Captain Lex
ander, Of the corps OF Typographical Engineers He
fully appreciated al the principles o. sound which have
given aud varied his plans Gnt all the required csndi
Tons, rs lar a. possible were fulnlled.
Oar Special Correspondence.
ALBAsr, Aus. 2l-A ".
The discussion last evening had one good vdc; pre-
vented people no,s.ng that the religious ceremonies In