New-York tribune., 1876-07-29
TYNDALL ON SOUND.
DISCOVERIES THAT HE IGNORED.

| IsIING KNOWLEDGE" DIR. DEIHAM'S "CELE-
BRATED PAPER" MlsQUOTED AED MIsAPpRE-
uESDED - BARON HUMBoLDTs AND PROF.
HENRY's PRIOR RESEARCHES IGNORED.
| TO the Edttor Of the Tribune.
SIR: II is known to the general reader that
scientific discussion has arisen between Prof Henry
the Chairman of the United States Lighthouse Board
and DR.. Tyndal the scientific adviser OF the Trinity
House in England with regard to the which affect
the transmission OF sound through tho atmosphere In
the last edition Of his work entitled Sound" Dr. Tyn
dali gives detailed account Of some very interesting
researches which he made in the year 1878, with view
the discovery Of these and the narrative his
researches is prefaced with what he calls Summary
of Existing knowledge" under this head before he began
his own Investigations That Summary" as follows:
While the velocity OF sound has formed the subject OF
refined and repeated experiment by the ablet phosO-
In the Philosophical Transactions" for I70S marks the
latest systematic inquiry into the causes which affect
the Elder brethren Of the Trinity House. and as their
scientific adviser, have recently had the honor Of
Gated one brief references will suffice 10 show
the state Of the question when ths h'cstgaon began.
Derham." says Sir John Uerschc found that fogs
and falling rain, but more especially snow, tend power
fully to obstfuct tire pIopaYon OF sound ana that be
snow on the ground. though when glazed and hardened
In very clear and able letter addressed 10 the Presi-
dent OF the Board Of Trade in 1868, Dr. Robinson OF
Armagh thus summarizes our knowledge o. fog.imals:
Sound the only known means really eroctiye bat
about it testimonies are conlcIlng am tarit eae one
tact relating its signal winch can Dc considered as
established Even The most important Of all ne distance at
ilnS al tisI5 & rs own currents
mtilul has & srsG as so fba1 a rnn or he'll which s6e1S
several miles down the wind is inandble poTe than iew
When hiost needed iog powerful damper o sound
DR. Robinson here expresses the uniyc sally prevalent
opinion and he assigns the theoretic cause Fog
he says mixture Of air and globnles OF water aud
az each OF the mnumerabe surfaces, when these two
fonch portion of the vibration is lost. Snow pro-
duces a similar efecs, and one stlIl lorc liJ rlou
Reflection being thus considered 10 take pace at me
surfaces of the suspended particles, It followed mat he
greater the number OF PARTICLES or IN other words tns
denser the fog the more injurious would be It's action
upon sound Hence optic transparency came to be con-
sidcrcd a measure Of acoustic transparency On thls
point Dr. Robinson, IN the letter referred TO- expresses
Al The outset it obvious that 70 make experiments
parable must have measure o the togs power0 stop
ping sound, without lending 10 which the most anomalous
bear some simple relation to opacity light that the
lay De taken as the measure. ..,,
"Sti clear arr regarded in this letter as the best
vehicle Of sound the alleged action OF fOgs. rai and
being ascribcd to their rendering the atmosphere
- discontinuous medium" ,,,, -,
Prior to the investigation now to be described, the
views here cnuncated were those universally enter.
tanned. That sound is unable 10 penetrate fogs was
taken to be "a matter of common observation" IEe
bells and horns of ships were affirmed mot 10 DE hrad
in fogs rs IN clear weather. IN the Ioss 9i Lon
don the Of the ctrag-WheelS was reported 10 DC
much diminished that they seem 10 De AT distance
of the existence of any other source for these opn
ions regarding the dcadcng power OF FOG thau the paper
OF Derham published 167 Years ago Ia consequence Of
their Il DrOTi probability, his conclusions seem 10 have
been transmitted unquestOned from generation to gen
Grafton OF scientific men.
The salient points Of this summary may De Diieny
recapitulated as follows:
l. That Dr. Derham's celebrated paper published In
l7Os marks systematic inquiry. and the latest one,
into the causes which affect the intensity Of sound
p That DE- Tyndairs inquiry designed to fill :" tho
blank" alleged by him have existed from l7oS TO tho
year 1873.
g. That fogs according 20 Derham. tend powerfully 10
obstruc the propagation Of sound; indeed, that sound
ia unable to penetrate fOgs was taken 10 he matter OF
common observation" after Derhams publication
f. That in consequence Of this supposed fact, and OF
its theoretio explanation "optc transparency came to
be considered Of acoustic transparency that
being a legitimate deduction from Derhams statements,
published l67 years ago." counting fron the date OF
Dr. TyndalPs writing
s. That prior to DR. Tyrdalrs researches, these views
were universally entertained" and had been trans
mted unqucs,ioned from generation 10 generation Of
scientific men," until Dr. Tynda arose in 1875 to ques
tion them.
purpose to contest the accuracy Of these historical
statements, which far from exhibiting the state OF
existing knowledge" on this subject when Dr. yndal
began his researches better suited 10 illustrate the
haste and superticiality with which his summary" has
been compiled
And. in the first place, with regard to Dr. Dcrhams
celebrated paper. De SoHi n0t published in the year
l7Os it seems proper inform Jhc general reader that
relates almost exclusively 20 its sujectmat;erfho
motion OF soandand treats only very inc!d ntally on
the intensity OF sound In aireatse of 81 pages only two
are directed the latter branch of the subject and
Dr Tyula had taken the precaution TO refer TO that
paper in ts Latin original as contained in the opening
part of tho 10th volume OF the Philosophical Trans
actions" instead of quoting it a secondhand from the
rasmcntay anl inaccurate citations Of john Icrsche
or from the nfcrcnces Robinson, he would have found
that far from being systematic inquiry" into tho
causes which affect the intensity Of sound, il prctends
- lon, ar,I .fxaN
soryatons temperature, weight Of the atmosphere
rain clear and focsy weather dense .ogs, ana
sdered in this relation. The. entire content Of Dr. Der
hams chapter under this head is as follows:
have often observed in the summer Time, when the
air has grown hot that sounds appeared more aucuid
sion the ear; while In weather az another sort
same sounds much piercing aud shrii, and
struck the more fOIc!by. Also Wn tho nGTtl or
southeast wind was blowing (lowcyer adversely /
have ob-eryed The sounds TO he clearer ANA ser rhan
If the wind was blowing from contrary quarters, ~
Krcher also observed Rome But this is uniformly
and always the case. Nor could l form any moro
ceraiu conclusions thc inspection rising Or fall
ms barometrr'aS had too confidently expected to 90
For discovered that sounds sometimes very clear
and shIil. sometimes very faint and an-Iid when the
mercury was rising TO the topi and, on the contrary,
sometimes very strong sometimes very weak, Wheh lno
obtains with regard to clear ahd osgy ar III RAINY aut
damp weather l have often observed that sounds are
bnicd ard that after toreutal rains they acquire the
greatest strength rs krcher observed al Rome but
The contrary also often happens For instance on
May d. 1902 Ihe ar a on l thi SGGiSn cya1 wa,
before TO have seen II. For such wac the prity and
Nlud serenity or the atmosphere that could cieary
and readily perceive exceedingly remote Objects But
ucycrIUvic was able 10 hear the ca non shat were
except a single one, whose thud. reduced to faint
sound, may lave caught IN my cllN) atnouSh cnIu
NJ tho sarc time the current OF the c.oud, and Of the
wind W., setting the same direction with tie sound
Moreover the breeze which then blowing WAS very
gentle such could scarcely r!c the hair; and N
nnc, all thing; nect s>ary TO promote the loree ana