The Hawaiian gazette., 1870-07-13


BEAcoSs AND SIGNALS Concerning the pos
sibility Of seeing artificial hight at a great Dis
tanee, the Ordnance Survey furnishes the most
interesting and Trustworthy experiences. Il 10
necessary, in the highly scientific details of such
a survey, that certain elevated spots should bs
rendered visible at great distances one from an
olher for the determination Of largs trangles Of
which the angles can be accurately measured.
The custom has generally been to wait for clear
sky aud then to employ powerful telescope to
view the summit Of n distant mountain. Whsa
Colonel Colby was placed in charge Of the IRISH
Ordnance Survey in 1924 he al once saw the Ne
cessity in misty q climate as that 0f Ireland.
Of employing some intense artificial light 70 rsn-
der the stations visible one fr1m another. Leu
tenant Drummond bad, shortly before that pssiod.
conceived the idea that the almost nnapproach-
able light Of ineandeseent lime, reflected from a
parabolic mirror might be used as a night bea-
con and Colby and he therenpon procee,ied 70
test the theory in practice 4 particular station,
called Sieve Snanght, in Donegal, had long been
looked for from Davis Mountain near Belfast
distance Of sixty-six miles. The mist day after
day, was too great TO permit Il to De seen and
then Colby determined to employ Drunmonds
light The night selected was dark and cloud
less, the mountain was covered with snow, and
cold wind gushed across the wintry scene. Col
by was on Davis Mountain. Drumm0ud on Sieve
Snaught; on the instant the latter displayed his
lime light, the former saw il as a brilliant star.
shining over the intervening Lough Nsagh. Il
was complete success Of beautiful experiment
The light was produced BY placing small ball of
lime, only quarter Of an inch in diameter. in the
focus Of parabolic mirror, and directing apoa it
through fame arising from alcohol stream
of oxygen gas; the lime became white bot Civ
ing out light, the intensity Of which alike sur
passed conception and description Il Is literally
true that tiny bit Of lime was visible axtysix
miles distant for it was not fame that was seen.
but the actual whte-bot lime itseiL The expert
ment having once succeeded. il vas applied in
various ways One Of the famous trianzies e.
tablished By Colonel Colby had for its three
points Ben I0moud in Dumbartoushire. Gains
muir in Kirkcudbrightshire, and mountain ia
Antrim in ireland each station vas rendered. By
the lime light visible from each Of the other two.
although the distances were sixty-seyen. eighty
one and ninety-ive miles respectively. ON an
other occasion he even exceeded hundred
miles, by this wonderful light
The ordnance surveyors have also succeeded IN
rendering their far distant stations visible n the
daytime, by peculiar employment Of sunlight.
Small pieces Of polished tin, specnlsn metal. all
vered copper, or lookinggIass, are 80 6xsd 10 ap-
paratus, that the suns rays may be rejected IN .
line leading to the distant station. where telss-
cope renders the rag visible Little Cleans of
sunshine have thus been rendered visible AZ dis
tancss exceeding hundred niles
Sea signals are being improved almost as de-
cidedly as land signals. A simple aad haadT
system Of dash-aBd-dot fash signals. for Use at
night when flags cannot be seen. hss been intro
duced into the navy. The electric light, the Iims
light and peculiar lamp which burns petFolssn
vapor incited by kind Of blOwpips. al have
been tried, and all are avasbls under diverse CIR
e6mstaDces, as well as Argand and other Iamps
The principle IS to give long flashes asd short
flashes the light being visible FOR greater or less
number Of seconds al tina Various modes Of
applying opaque screens add Other tsnponry
obstacles have been adopted to regulate he a.
ternstious Of long and short flashes; bet, when
once adjusted, and properly worked, the long asd
short flashes are translated into nautical words and
phrases By means Of dot-and-dash eodesook-
Two ships are thus able to speak With each
other at night when several mics spast and "A
admiral commanding feet may be able - sig-
nal to every point Of the compass at ooee, b.
using what IS called an ali rOund Hsht-47
Ese Year Round .fl 3l1 81