The aegis & intelligencer. [volume] (Bel Air, Md.) 1864-1923, 1900-05-25

reaches the sea at Norfolk and Cape
Henry. Its path then crosses the
Atlantic Ocean and touches Portugal,
Algiers and North Africa, and will
terminate near the northern end of
the Red Sea. The eclipse will last
minute and 12 seconds near New Or
leans, and 1 minute and 40 seconds
near Norfolk. 1t is probable that
large numbers of people will take the
railroads to points where the eclipse
can be seen. A number of experiment
tai stations will be established by the
government along the path OF the
eclipse. The necessary apparatus Is
now being gathered and arranged,
and men specially adapted for the
work are being engaged and are
trained. Congress has allowed 5000
to the Naval Observatory and "a 900
to the Smithsonian Institution for
this purpose. The Naval Observatory
will send out two expeditions. They
will probably be located in North
Carolina and Georgia, 200 miles apart.
The Weather Bureau is collecting
years in the month of May for the
localities along the line of totality. 30
far they show there is less chance of
cloudiness in Central Georgia and
Eastern Alabama and this is, there
fore, the best region for locating the
eclipse stations. The stations will be
occupied two or three weeks before the
eclipse, and the part which each man
will take will be thoroughly rehearsed.
It is very imperative to make no mis-
takes during the minute and a half
when observations can be made.
The Smithsonian Institution officers
will be under Prof. 8. P. Langley,
those Of Princeton University under
Prof. Young, those of the University
of Pennsylvania under Prof. Stone,
and the Yerkes Observatory will con-
duct the expedition with Prof. Hale
at its head. Nearly every college and
scientific institution in the country
will be represented, and probably 100
expeditions will observe the eclipse in
the path Of totality in addition to
large numbers of scientific amateurs,
who will make extended observations.
Prof. Brown, Of the Naval Observa-
togy, considers that there will proba-
III be thousands of these unattached
i.mateurs. 1t should not be forgotten
THAT one of the finest sets Of photo
E:a phs Of the eclipse in India, in 1896,
was taken by an amateur with home
cat by the Naval Observatory will
consist of only five or six observers.
The same observatory has issued a
little pamphlet containing a map of
the path of the eclipse showing the
various towns, railroads, streams and
elevations, and it contains suggestions
for observing the eclipse.
Photographs of the corona are OF
great scientific value, and may be OBJ
tanned With instruments Of moderate
dimensions. Almost any good rectili-
near lens may be used. One with an
aperture of 81 inches and Of a focal
length OF 32t inches proved very
satisfactory in the Indian eclipse ex-
petition of 1898. For plates OF ordi-
nary senstiveness exposures OF one or
two seconds are ample. 1t is better
| to use O plate OF normal sensitiveness
instead OF an extra rapid one, and to
lengthen the exposure in proportion,
because q slower plate is easier to
handle and permits Of q more re-
stricted and prolonged development
and is less liable to accidental logging.
Photographs taken with amateur in
struments are, of course, not as val
liable as those taken with instruments
| provided with a driving clock or
other device for keeping the image
stationary on the plate. In focusing.
the instrument should be pointed at q
well-defined object distant say from
one-quarter OF a mile to mile, ana
| the object brought to a short focus
for center plate, The image OF the
sun ia really small object and occu-
pies but comparatively small part
| of the center of the field. The focal
length of the camera in inches will
| give roughly in diameter Of the suns
| image in hundredths Of an inch.
| Negatives should not be retouched.
While proper telescope Is desirable
small spy-glass and opera glasses may
be used. For the first and last con-
tact shade glasses are necessary.
The usual and most Objectionable
color for a shade is red, either q neu-
trail tint or green should be used, and
deep blue is also recommended. In
struments specially intended for OBJ.
serving the sun are also provided
with arrangements for getting rid OF
the excessive light and heat without
diminishing the aperture. and often
without using shades. Special care
must be taken that the temperature OF
the tube is the same as that OF the
loutside air. The first contact is a
slight indentatlon in the suns limp,
and it usually attains some size before
the observer, unless he is specially
trained. sees it. The internal con-
facts, or beginning and end OF total
itv are phenomena of such a definite
character that the instant of their &C.
currence can be noted within a small
J fraction of second. For a minute or
two before the predicted time OF
second contact the sums thin and
now fast-waning crescent should be
carefully watched through a neutral
or green shade glass. Presently the
crescent will become mere thread OF
light, which will rapidly shorten ana
suddenly disappear. The approach
of the third contact will be heralded
by the rapid Frightening OF the
chromosphere at the point OF the
moons limb, where the sun is about
10 reappear, and two or three seconds
later a sudden burst of light will an
o>unce the contact itself, and with it
| .'se termination of totality. The OBJ
.aryation OF the fourth contact is a
,imple matter. The segment cut out
If the sun by the retreating limb OF
the moon is carefully watched as il
becomes less and less, and the instant
Of its final disappearance is noted as
the fourth contact. Very precise
: directions are given by the Nava
Observatory authorities for amateui
, teIescopic observing parties, and are
4 4