New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1873-10-29

=. IL. Z.
Prot J. NJ. Crgfs, Trot' ~ Su{ Dc,
II u "T yi''SSorc ain Irof G.. j. Brush.
n ~, fnScrS Ueprv PROT w z. Trowbridge,
Dr. ! n UiIeard ID. J. Hammond Truinbull.
P Plo{ Sli ne NJ. Mayer, Prof. W. A. Norton.
Prof. bCuamlu Pcrct, - > =. NoWD' -,
Prof. Bcuilmin Sihman, PiOi fdirmah Rogers
The venerable Prof. Henry Occullcd ue o"dI' u'u
read the opening paper;
so,,yp IN RELATION TO FOG slGNALs-BY PROF.
JosrpH HENRY or me SMITHSONIAN NsTTU-
TON,
Tho coast Of the United States, the commercial coast
Is the longest in the world II exceeds ten thousand
miles on the Pacific the Atlantic, and The Gull States
Aud a very portion Of this, particularly az the
northeast and sOuth-west, is affected by fogs When
ever the wind Is from souherly direction, 1t blows
across the Gulf Stream, and watts the heated cir from
that quarter the cold polar current which sets
IN between tue Gulf Stream and the coast THIS brings
air OF different temperature and one charged with mos
ture INTO contact that the two are mingled and FOG
Is the result 10 therefore became OF great Importance
70 inquire as TO the best signals 10 warn the mariner %
danger along very dangerous coast.
T1eIashi- House Board of the United States has from
is first establishment aimed only to furnish sea
coast with an the aids to navigation that have been
suggested By the experience OF other countries and 70
adopt nc latest improvements, hut also TO enrich tie
light House service with the results Of invcsgl-
tous and devices Tor the Improvement OF its ED
Cleucy o. other words to aud IT'S share 70 the adj
vance q! SIGN NiiNu III t"h9 1" wv wants VI wv
highest civilization
Among the distinctions 10 navigation none are more
serious, especially the AlnereGE coast, than those
which are caused by fogs.
Fog, a. is well known, due 20 tle mingling OF warm
air surcharcod with moisture with colder air, and no
where the surface OF the earth do more favorable
conditions exist for producing fogs than both on orr
Atlantic aud Pacific coasts On inc Atlantic the cold
stream Of water the Polar account of
rotation Of the oarh, passes southwark close
along our Eastern %coast from one extremity
to the other and parallel with this for
considerable distance is the gcoat current OF warm water
Known a. the Gulf stream. Above latter the is
constantly suIchargcd with moisture, and consequently
Whenever a breeze or hight wind blows nom the latter
across the former the vauOr condensed into fog aud
snce ga Summer along eastern coast the sOuthery
wind prevails We have during July. August ami Sep
tember an almost continual prevalence OF logs dense
that distant vision is entirely Distracted.
On tire western the great current of the Pacific
after having been cooled IN the northern regions III its
passage southwark gives rise TO cool and water
~ juxtapo.iton or. in other words current of the
former through the latter and hence whenever wind
blows the current of cold water fog produced
From te going statement IL s evident that among
the aids navigation fog signals are almost as i'm
portaut ne lighthouse apparatus The application, how
ever OF the science acoustics TO the former sar less
advanced than is that Of optics the latter. Indeed
attempts have made 80 apply lights OF superior
penetrating power such the electrical and the calcium
light. to supersede the fog signals now in use WEcn'
however We consider the fact chat the absorptive
power q a stratum Of cloud, which Is but a
lighter fog perhaps not at most of over two or three
miles Do thickness is sufficient to obscure the rays of the
sun me intensity Of which are greater than those OF
any artificial light IL must De evident that optical means
are inst rcient for obylating the difficulty IN question
Tic great extent Of portions Of the coast OF the
United States which subject 10 foas renders the nves-
ugaOu Of the subject of fOgsgnas ono OF the most I'M
portant duties OF the Lighthouse Board.
In studying the sublec: OF fogsignas II becomes a
question Of importance 20 ascertain whether waves Of
sound Ike those Of light absorbed or suhed by iog
On this point, however, observers disagree AT hrst
sight from the very striking analogy which exists ID
many respects between sound and light the opinion has
largely prevailed that sound Is iDpcoed By log. CD
servers however who have not been Influenced by tns
analogy have IN some instances adopted the opposite
opinion that sound better heard during foe than IN
clear weather
TO settle definitely this question, the Major Elliot
Lighthouse Board and self have directed that at two
lighthouses Cd the route from Boston 10 ST. Johns
the fog signals shall he sounded every day on which
the steamboats, from these parts pass the station
both m clear ana foggy weather; the pilots on
hoard these vessels having for small gratu
NY engaged 10 note the actual distance OF the
boat when the sound is first heard on approaching the
signal aud Is lost receding from IT, The boats above
mentioned estimate their distance WIN cOns!deIaOe
precision by number OF revolutions OF their paddle
wheels recorded by the indicator, aud II is hoped by
this meaus TO decide definitely the point in question
We think IL highly probable that fog does somewhat
diminish the penetrating power OF sound or ID other
words produce an analogous effect, 10 the case OF
light. Bot when consider the extreme minuteness
~ the particles Of constituting the fog com
pared with the magnitude OF the waves OF sound, the
analogy does not hold except IL minute degree as
70 be Of practical importance or other words the
existence Of fog true bur, think insufficient cause
OF diminutioD Of sounds.
Another cause, which without doubt Is true one. OF
the diminuton OF the penetrating power OF sound Is
the varying density OF the atmosphere in long distances
The effect o. this, however. would apparently be 70
dOr slightly the wave OF sound rather than 10 oblit-
crate IT, However this may he, we think from all tho
observations We have made the effect Is small In com
pArison with another cause viz that Of the influence
wind on the Transmission OF sound During residence
Of several weeks at the seabOre the sound Of the break
at distance OF about mile appeared IN 10 case
o. be coinedent with the variations of tho aueroid
barometer but in all cases affected by the drec
ton Of the wind The variation in the dstfnctness OF
the sound Of distant Instrument depending the
direction o. TIC wind is 30 marked that we are war
Ianted In considering " the principal cause OF the IN
Efficiency In certain Of the 100T powerful log sig
hals The effect Of the WIND Il usually suho1. .
AR bet the nearer and the sounding ihsfuneh'.
IL the eae Of It, cOuuBg toward bin the velocity OF VIE
sound being reinforced by thar OF thc nOuOD OF tS
aud when IN ans opposite direction IL being retarded
"a an equal degree. little reelection, however Wl
show that this cannot the canse OF the pbehoheho
10 question siuee the velocity OF SOUND Is 20 shsty
greseT tsu thar OF any ordinary wind, tat the hitter
ran only impede the progress OF tio FORMER by WIZ
snai percentage Of the wbo'. IIS' ssohes ~, %
Idmbfdce University, E1glaud, Gas Oheied very ~,
tshlOuk hypOt cc piauatiOu OF TINS eueCt OF Whu