The semi-weekly messenger. [volume] (Wilmington, N.C.) 1897-1908, 1900-05-18

AlG
works on optics, but I am unable to
see how any such regular and SYM
metrical distribution OF light and shade
can result in this way. That the dis
lance between the bands varies on diff
ferent occasions lends some PLAUSIBLE
ty to this explanation, but 1t is not
impossible that the width of the bands
Is a function of the location of the
point of observation. that is to say of
its distance from the center of the
eclipse track. This al only be de-
termined by numerous and extensive
observations covering a wide tract Of
country, and it is to secure Is many
data as possible on this subject that l
desire to- secure the cooperation of
all who are interested in the subject.
observations just outside of and Just
within the track Of totality will be of
especial interest. The observations can
be made without any apparatus. and
as the bands are not visible during
totality, their observation will not in
convenience any who i more inter-
ested in the spectacular than in the
scientific side.
I desire to secure, if possible, a COM
plete record of the appearance of the
bands yer the entire country, togeth-
er with statements regarding the direc-
ton of the wind, condition of the air,
etc. The bands can be best observed
by spreading a sheet or other large
white cloth on the ground. AS soon as
the moving shadows appea which XII
probably be about a minute before
totality, lay a lathe on the sheet paral-
lei to the shadows, with as great &C
curacy as possible. Then try to es-
timate the width of the bands. and he
velocity with which they are moving,
also the direction in which they are
going, that is whether from eas 20
west or VrQSt RI aaCt Tho xridtL "a +La
bands car De best determined. I mag
inc q have never seen them), by esti-
mating the width of a group, saw five
or six, or as wide a baunch as the eve
can grasp and follow with certainty
as to the number of dark bands in it..
A scale for reference, preferably a
white board with feet and half feet
marked with strong black lines. will De
of assistance. 1t should be laid perpen-
dicular to the shadows, that is at right
angles to the lathe. The speed can be
estimated by trying to keep up h
the moving shadows, and may he re-
corded as slow walk, fast walk. slow
run, etc: Those who are accustomed
to counting quarter seconds, can prob
ably make a fair estimate of the sre-d
by noting the time of transit OF . ia~d
across the sheet. The shadows Will
disappear at the moment Of totality,
but will reappear again as soon as the
suns edge emergeS from behind he
moon. A second lath should be =
on the sheet, parallel to the bands un-
less their direction is the same. and
the same observations repeated. noting
whether the direction of motion is re-
versed. After the eclipse is over. de-
termine the direction of the two laths
as accurately as possible with the COM
pass, and measure the angle between
them. Note the direction of the kind
before and after the eclipse, and record
the general atmospheric conditions.
BEFORE TOTALITY.
1. Direction of the bands.
2. Width of bands. (Give all data,
that is, number of dark bands in given
width of the system.)
3. Estimate speed. State how esti-
mated.
4. Direction of motion. Whether from
east to west, or west to east.
3 Genera appearance. Whether sharp
or hazy whether contrast between light
and shadow is considerable. If posi-
bic estimate relative intensity of i1lu-
in lark and light areas.
6. Direction of wind. Temperature
and general atmospheric conditions.
AFTER ~TOTALITY.
Repetition of the above.
Actual angle between the laths.
General remarks, and location of
point of observation.
Reports Should be sent to Professor
R. w. Wood, Physical laboratory OF
the University of Wisconsin, Madison,
Wisconsin.