New-York tribune., 1876-10-24
ACADEMY OF SCIENCES.

PHIIApELPHIA, Oct. 20.-Tallng the vlbra-
tions OF matter single subject, large proportion "
this years work Of the National Academy OF ScIenoes
could be grouped under that head But perhaps solie
wiseacre might say with show OF proprieV 'na' al
Natures work consists vibrations OF matter lnere
a. bowever n more direct relation between the four
essays here presented Of them dealing win theories
OF light waMes and two with theories of SOUND waves
PROT s. p Langley, the astronomer OF Ahegheny w.
servatorv WAS 10 have read the hrst paper he u n'
read II because he had lost his manuscript ain not
srr that have ever heard of previous instance where
sneaker had lost his manuscript and could not lay 'e
nnc an some newspaper man. The loss prevents any
thing more being given than an informal resume OF MS
importan experiments and their results Inc ne" ais
coycres of Prof Henry in relation to the laws OF sonnd
are among the most important scientific works OF the
mast wear whether regarded from the point OF view OF
theory or Of practical results Prof Roods novel exper
imens with the radometer will add new evidence that
that scientific whrleg is not propelled by the direct
impact OF rays Of light.
SIN LIGHT COMPARED WITH THAT OF THE BESSIE
MIR FURNACE.
On no ono of the unsettled questions Of science there
80 wide discrepancy in respect to the values set on
the actual heat Of the surface Of the Estimates
have been furnished by Hersche and Secch that place
at 10 600 OOOo; by Ericsson 4OO0OOOo and on the
other hand hv French ply yscists Of Tcpute at point t
tic over that OF blast urnace-say l5OO0 cehugraue
This is a monstrOus discrepancy for skilled experiment.
ers The difference results depends upon the mode OF
working the problem and the assumption involved Inc
large estimates come from following Newtons law that
tcnperature increases radiation does Inc smaller
estimates from applying Dul0ng ana Pett law
in which temperature is function of radiation fme,
tion that reaches s pFaencal extreme "nch II 'S P
beyond temperature OF 2,OOOo. ,.
Strange say, the direct and simultaneous COMPARISON
of thp sun heat and that from terrestrial sources mas
not vet been made As approximate mode OF inquiry,
Prof s p Langley determined to compare 3io re- teg ~ & Ui
the sun that from the molten iron poured O OF w
Besscmer The experiments were ma1t a' Ie
Edgar Thomson Steel Works, where every facility was
given Tie galvan0meter couIu no, u. useu ., IU - ~,
Ing comparative heats, because that lhStTuhenI Il Il,
once affected by the movement OF large masses q" IRON III
Its vicinity. The lltche type OF pholoc,i ord
ployed Prof. Langley described lts construction anu
merits In HsnS u ne wa & avTu i'm t U"ston of the
BcssemCc converter. The hcliostat aangemeht 10 ,e
ally shifted the observer sat on WlhlOW slII m u
comfortable proximity to the furnace 9pcia.IoIs p, h
given here. Tie first conclusion reached eage IVA, was
that the suns light which turns ine ai nse least S0
times the greater Then the seciI0'cpe was empioyJ
and the two rays compared Inc Sttei ray & W. Of I it
"a times brighter. Next Prof Langley ln'ic con'd, @
sons of the suns with those from the hhc anoNc
The converter when the latter at their brightest
This was less difficult proceeding ana iufhlsAeu noe
specific results The photometric comparison co4u % ne
/ light may not be quite bright az that OF the
/ molten steel. The aranscment was .ohe"nht ,,
| like that Of camera Ohscurl II gave ihe
image Of the accurately hat sun spots couu We
easily examined; u also gave an eNact r m
the furnace flame. Each was alternately supeipou o
the other The conclusion Is that the sush Is ~ IN ~
21Gs times brighter than the fulIlee nane As Iii ,i
heat presumably Of the same reiduNe oider te i S
is adverse the law OF Dulong and Ieut Ine achs t
heat is probably among the hgher values 'h"'
have been suggested
SOUND Al SEA.
Prof Henry merely proposed TO communicate some
additional facts obtained In his longconuhued an"
elaborate researches concerning sound in relation To FOG
signals During the past year his dates in connection
with the Centennial Exhibition prevented his giving a.
much attention to the subject in previous years ls
principal investigation tins year hau reirItuGe 10 |
OF sound especially ds 10 TIC ph'Hv''''u"
known AZ the ocean echo. lie had shown III previous it
searches that loud sounds are wanting ia analogy TO let
so far concerns obeyngis rnle mat ihe aus'' y. @
deucc cquaed by the angle oi releeuon. Io".s ,
rr if Seam Of parallel rays diverge IN all directions
n was found ia the of parabolc reflector o tWel
the sound was somewhat greater at tue dlStahcc oi
mile in axis OF the ref ctor than elsewhere v az
distance OF four miles the sound had 80 dyergcd that
reache9 tv uoe no. d IN tbc front Of the mirror The
cause OF this divergence Is not dincut 10 cOhG'.c
| W., euluose tie crest Of wave OF SOUND tn j..
briniit terminated AT either extremity, the tendency
az tr c33npressed air which constitutes the wave " be-
10 exuand Itself in l dircctonsatealy irou ilt tuS
of the wave as well directly in front Anohcr cause
NAV probably be found in the rttatlon 0i te Two ,uS
of the wave il proceeds from the mouth Ol lt rum
net This would occasion curing o inc emu W thS
wave AS well as IN cOugatiOu OF them az they proceed
from the spreading mouth OF the instrument ~ tn'
tendency of sound 70 spread 20 DC louha an Sa p p
ZION OF the acton of trumpet BY conning the soud
that tendency is temporarily overcome ,he tule, m sH Nv
iag TO the beam OF sound greater h'a m
axis and thus checking the spreadns Hence u mail,Is
"A
! as one with interior OF polished metal. .u
Athough the tendency OF sound Is to diyerge IN All
hot NAV he called sound shadow Is produced For
instance, let Ogslgna be placed al OF near
on one side OF island that mas cOlcdl eIcNa'ion'
Tbpn the signal will be heard distinctly by vcscl Oh
fEe OupOslte side of the island ~ distance OF thiec
signal being the opposite sidej, the sound WIN be en-
tirey lost when the distance II reduced TO lne ana IN
ann smaller distance IL Is not recovered III TINS case te
saom d oi badnV The termination Of that shadow is
sNI
over the crest OF the island bend down ana re'ch 'c
Prof Henry suggests that the ocean echo may be ex-
planned the same principle Ihl' echo CONSISTS Ul
revcrerton coming from the horizon, near the surface
nf tLe ocean aud from around point IN the prolong-
ton of the axis OF the trumpet Prol lyndIl aulDuTs
the echo to reflection from the air Seltlom lNlspe
acoustic couds OF different density near the horizon
1t is that reflection Of sound rom portion Oh a
of different density Is possible Fi3' Iyhu'' me suo"
by experiment tnat an echo may be given from sur sur
face Of But the reflection IN TINS case was pro
duced by an ain0, iheic ia an I, ,Id ~
this scarcely furnishes an instance Ol Nhl cum 'he
place III ordinary atmospheie' Iio @ heiS az & ~. M ~
r!bued these echoes 10 IenIctoHs u Ol 'ne ,i
ocean waves, but he now thinks that ny an apcttlon
ton Of sound the phenomehon may og eAr"n'u rrfn
reflection from the perfectly 5lnpotm Uatr yn
| by Prof Tyudall, requiring reflection from the
air the trumpet Of sired was turned Directly 10 tle
was heard from the proOngatO of the axis Of tne trm
| pet e., from the zenith. loud echo was, however
heard from tne whole circumference OF the bOrz9nLna
of which was on land the other half water Ihs was
repeated many tncs and always win me same result
the zenith. from which few drops OF rain fel
/ into tine mouth Ot the trumpet; stll no SOUND was
heard from the zenith, although sound continued
TO be heard from around the horizon. In inns
case on account divergence of sound, portions o
waves in every direction must have descended 10 lhe
horizon; aud of these must have reached the
nlanp of the ocean In path cuyng inward toward the
source Of sound they wUld whep they reached tne ear
of the observer In the vicinity Of tine source seem hs
# coming from point in horizon, and hence would
give rlsc TO the phenomenon OF the ocean cch0 Rays
Of souud at different distances from the ear wolld be
Tected from the surface of the ocean, and thus gave
rise TO prolonged echo. This Is In accordance with the