The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1878-05-06
MERCURY'S TRANSIT.

HOW THE PLANET WILL TRAVEL OVER THE
FACE OF THE sUN-soME FACTS ABOUT THE
TwINKLER HIS MOTION AND APPEARANCE.
To-day the planet Mercury passes the SUMS
disk, little to the north OF its centre; that Is to
say, the Garth, Mercury and the come in line
that small area of the lace Of the latter is obscurcd
by the intervening body OF Mercury This is called
transit OF the planet and Is in every respect similar
TO that performed by Venus when she assumes
respondn position with relation to the earth and
There arc only threo OF tho heavenly
bodies that come between the and tho
earth to pcrcept,siy obscure all a
portion Of tho solar disk. These the planets
Mercury and Venus and satellite tho moon. Mer-
curry, by It's motion alternately becomes morning
and evening star oil washable brilliancy but emit
ting peculiar twinkIng light OF all the planets he
10 nearest to the sun, aud completes hts revolution
around tho great central uminary exactly 81 days.
% hours, Is minutes and 40 seconds But tho
earth moves in the same direction around the sun,
the apparent time OF revolution Of Mercury is much
longer than that above given
MERcURY's LIGHT MorIoN
Mercury, like tho moon, receives his light from the
sun, his brinancy is therefore borrowed; like the
moon, also, he presents to tho observer different
phases from the full disk TO the thin crescent Tho
former exhibited whom the planet Is ON tho oppo-
sito side OF the to earth the latter when ho
o between the earth and the SUM- In performing is
orbit which ia very eliptica, Mercury travels
at the ratio OF twenty-sight miles per second,
or 100000 miles per day. At his greatest
distance from tho sun II Is 44,475 900 miles away
from that luminary. At its least distance 1t is
20 305 900 miles. The Intensity oflght which Mercury
from the at It's distance is 6.G7 tmos
great that with whc the earth Is illuminated
under similar conditions Of distance. Ho therefore
md which ID, OF course seven times greater than
that received by the earth Mercury turns on his
axis IN twenty hours ana nve half minutes
consequently tho length OF tina day In Mercury Is
about equal to that tho Garth but the inclina-
ton Of The planets axis Is very considerable with
lation to the plano vi IT'S orbit extrome alterations
OF heat and cold must be experienced during revo-
luton Tounh the sun.
THE APPEARANCE or MERCURY.
Owing to the proximity of Mercury to the sun II Is
dific ut with powerful instruments 70 observe
tho character of his suria CO. An equatorial
band is, however, worry distinctly defined tho
planet and during its phases serratod edges mark
the presence Of mountainous inequalities similar TO
those observed on the moon. From calculauous
OF Mercury Of enormous height. one being esti-
mated ut eleven miles. The observations To-day mace
WI, wsn ., sne owsu a.
largely increase Qua knowledge OF tho peculiar form
oil Mercury. As explained Ia yesterdays HERALD it
will be possible TO measure with great degree OF
curacy both the equatorial diameter and the polar
compression of thoepanet. Some light will also DO
throw the SUBJECT OF the atmosphere OF Mercury,
and, lastly, the existence o; satellite satellites,
similar TO those recently discovered In attendance
Mars The long duration OF darkness alternately
In the homspheres OF Mercury suggests that n tho
plane. s inhabited bcIngs by ike man, the light Of
one or more satellites may DO enjoyed by them
WATCHING THB TRANSIT.
The fact that astronomers will watch tho face OF
the to-day through great telescopes. fitted
m al nj % m mn hmm
Tor regulating the motion and direction the mstru-
monts need not discourage tho amateur his efforts
TO obtain q view OF the transit Little faith DO
put In piain smoked glass, as IL possesses mag.
nifyiDg power, but ordinary opera glasses small
telescopes can be employed with great advantage N
the eyes arc protected ny smoking The giasses Any
one desrous Of making careful observations should
regulate them by correct watches clocks From
tho mass OF Information Obtained in this way tho
astronomers At Washington anu elsewhere may mako
some useful deductions. NO person therefore VINO
observes the transit with ordinary should negect
10 forward the results concise form The Naval
observatory, washington, as soon as possible. With
powerful glasses the number, groupings aud character
Of solar spots might also be observed with advantage
Tho weather Will probably DO favorable In all Of
the country west OF the Alegnany Mountains and
south Of the ONO Valley, SO that a very extensive
area Tor observation Will be availod OF.