Los Angeles herald., 1907-05-26
Sundials

IMge8I style erected on its surface. This
SsstSS was probably the first method used
+h.+ - : 70 note the. passage OF time, ana
1aet that Isaiah mentions it.
nj Oials are found all round the world. In
Ghrstian =; mIn countries the churches have them;
~ ~ Mienammedan countries the mosques have
ttnem; IN Buddhist countries the temples haVss
them And they are Of all kinds-some meas
g ulIng time by, the direction of the shadow,
o.,ni oUtle 3y its length; and the length varies
tty etSety DAY, 1t being fact not generally known
t1 tnat IN latitued 80 degrees north a stick two
noon on June a. and one seven feet long at
noon sp on December 2
a., he essential of all modern dials is that
naraIIog raT IeIGge OF the style or gnomon I, must be
o5n c5 horizontal, as on pedestals; vertical as on
Gu Snurch Walls-one of the best of these is at
~, 5;", Marys, In the Scilly Islands, where the
ttal ia Is on an old gun; declining vertical when
Vhe gnomon Is placed santingly, owing to the
outlook not being due south; and round.
VI all the varieties of dials the inventors
are are known. Dionysidorus invented the cone,
i,i hasrocles invented the pelecinon, Theodosius
ala'eneed ~ tLd the pros pauclma, Parmenio invent
ea The prosta istoroumena, Scopas of Spra-
cuse invented the plnthium, Apollonius in
Csnged the aranea or aracuhe, Berosus the
Chaldee invented the hemicyele followed into
q a square and Aristarchus of Samos invented
the caphe or hemisphere.
Ihls was the commonest Of the old dals.
IL was cut out of block of stone, with the
sIyle on the top, in the centre of sphere, SO
tnat the shadow travelled along the arc of
circle similar to the diurnal parallel of the
sun.
IL was one of these dials that was dug up
out OF CIceros old house at Tusculum in
l741, and which is now called by his name,
and said to be the very dial he alludes to in
a' sl The Ofan time 'ne @ayay, THS'0b but stir not"
Qf the spherical dials there is specimen
in Portsmouth dockyard in England, and Lon
don once boasted a very fine one in Lead
enhau street. 1t was globe on the top of a
lofty, column, from the Tyre on the capital of
which spouted ten streams of water.
we may quote the way in which it was
"To make a dial upon a solid globe that will
show you the hour of the. day without a
gle:n gnlo:mon: The equinoctia!! Of this globe.-or,
divided into twenty-fo equal parts and
ming again with /, 2, 5, 4, etc, to II.
Then, if you elevate one of the poles so many
of the world is elevated above the horizontal
in your habitation, and place one of the
twelves directly to behold the north and the
other to behold the south, when the sun shines
halves the. one enlightened with the sunshine
and the other shadowed And when the end
lightened half is parted from the shadowed
half, then you will find in the equinoctial the
hour of the day, and that on two places on
the ball. for the equinoctial is cut in two op-
posite nointse by the light of the SUM-"
1t is quite likely that some enterprlsing
boy would like to make sun-dial for his
own instruction and amusement. IL so, he
has very difficult task before him, as the
construction requires good deal of mathe-
matical science.
Ii we resided at the North Pole of the
earth, the construction of sun-dial would
be extremely simple. The sun there moves
around the horizon at q nearly uniform
height, and we should then say that, as the
sun moved 800 degrees in "a hours, it would
move Is degrees in an hour, OF. degree in
four minutes. A common circle, therefore,
with an upright in the centre, would answer
for sun-dal
But in any other part of the world, this
simple rule will not work. First, the exact
latitude must be found, then the dial must
he laid off in lines representing the divergence
of latitude, then style must be placed so that
its shadow at high noon will be cast due
south.
All this requires great amount of COM
YOU have sun time, which varies from true
time every day in the year except two.
A night or nocturnal dial is an instrument
for showing the hour of the night by the
shadow Of the moon or stars. Moon-dials
NAV be constructed relative to the moons
motion; or the hour may be found by the
moons shadow on the sun-dial by the fol-
lowing rule:
Observe the hour pointed out by the moons
shadow; find the days of the moons age in
the calendar; take three-fourths of that num-
and it will give the hour of the night.