The daily gazette., 1882-12-06

| prevail. With the MercuriaI transit we
have a coarsely divided scale to measure
a small angle, In that of Venus finely
divided scale to measure large angle.
Two methods are adopted by astrono-
mers in ascertainisg the distance of the
earth from the sun by means of the transts
of Venus. Stripping them of complex de-
tails 1t may be explained that the method of
HALEY, hither to In use, consists In selecting
two stations nearly on the same meridian OF
longitude, but separated by as wide an in
terval of latitude as possible, and then OBJ
serving the separation Of the apparent
| chords described by the planet as seen from
the two stations, which will of course be in
| proportion TO the distances between them.
| Theoretically only two stations are required
| for this method, but in practice 1t is found
| essential to have multiple observing stations
to ensure observations at one place where
| unfavorable atmospheric conditions may
prevail at another. In this manner the OBJ
| servations at Chill might be compared with
those at Connecticut and so on.
The Delislean method which is preferred
by modern astronomers depends ON the fact
that the motion of places ON the earth's sur
face from West TO East In its axial rotation
being greater at the Equator than towards
tho poles, the planet Venus in transit will
appear to move more swiftly across the disc
same reason the transit will begin later and
end sooner in some parts Of the earth than
in others differently located. A careful ex-
animation shows that in the United States
the entrance of the planet on the disc will
be accelerated and its egress retarded to the
greatest possible degree, while at a point
within the Antarctic Circle (Sabrina Island)
the opposite conditions will prevail. In
fact, sabrina Island is the only point suita-
bic for the corresponding observation.
The following is the distribution of the
principal stations Northern Hemisphere
Canada /; the Atlantic Seaboard of the
United States New Mexico, Texas,
Canada Southern Hemisphere Chilli,
New Zealand, Patagonia, Cape of Good
Hope, Australia. In the British Isles and on
the Western Coast of Europe and Africa,
only the beginning Of the transit will be
visible ; in the far Western States, Australia
and the Pacific Ocean only the end. In
Eastern Europe and Asia the phenom enon
will occur during the night and of course
be invisible.
The comparisons of the results of all the
observations, by photographs and by instru-
mental observations, obtained at perhaps
100 different sources and embracing possibly
l 200 items, is work which can hardly be
completed within the next ten years,
although its results may be approximately
guessed at within q much earlier period
just as the negative obtained by photo
grapher goes through multitude of delicate
processes before the effect appears as fin
ished picture, SO numerous, exceedingly
complex calculations, additions, deductions
and corrections have to be made in each and
every observation before it can be used as
an element in the final grand calculation.
The work ofrevising and reducing the OBJ
ecrvations of 1874 is not yet completed and
the data then obtained were few III number
compared with those expected to-day.
The appearance of the sky at sunrise in.
dicated the probability amounting indeed to
certainty, of a favorable day for observing
the transit. With a very large number OF
persons the early morning inquiry was
'What is all the fuss about Z" They looked
at the rising sun, but Cnothing appeared par
ticularly the matter with the monarch of
day; as he rose majestically through the
banks of stratus cloud.
At 0 O'Clock, however, curious individuals
appeared in sundry doorways, investigating
matters with pieces of smoked glass, but
discovering nothing unusual they muttered
something about newspaper frauds" and
returned to their usual avocations. 1t is but
fair to say that the vast majority of those
who used such primitive resource actually
saw nothing OF the transit. The disc was
too small to be seen successfully by any but
the keenest eye.
The telescope used by the writer was
quite small one-"a deer-stalker"-of IL
inches aperture and power of 25. At 9.15
the planet was just visible as a notch in the
lower limb of the sun at little to the left
of what would be termed the South Pole on
Map OF the World. At 9.23 a. IN. it was
lust connected by tiny ligament Ito coin
a term) with the suns edge and at 9.25
stood completely within it as in figure l.