Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1892-08-06
RICHES OF A CONTINENT

Would be Needed 10 Construct sigma That
Could De Seen on Mars-rhe Difficulty of
Commuuication-AD Difference in the At
mosphere.
CHICAGO, Aug 5.-Prof Elias Colbert,
an astronomer who has made the science a
lifetime study, said tonight:
Mars will be nearest to the earth Satur-
day next the distance then being but 3d. I00-
600 miles. The opposition occurs a little
earlier, but it will not then be in the most
favorable position for study, being too near
the eartls moon, which will pass the Planet.
leaving it a little to the south. about 10
O'Clock Sunday night. The moon being near
the fufL her light will interfere with the
dy o. the markings on the surface O!
Mars for tw61pr three days before and after
conjunction, 50 shat it may be said that the
first hall OF the Adorable time for studying
the planet has already gone by. The fifteen
or twenty days following the early part of
next week will include about all the time
during which Mars can be studied to the
best advantage.
The limit of visibility of objects on the
surface of Mars is a subject about which the
mind of the average man is little hazy and
little precise information on the subject is
at his command. 1t is stated that a magni-
fying power of 1000 will practically bring
the planet within distance OF 1850 miles
from the earth at the time of tile nearest
approach, the meaning of that being that
Mars will be seen plainly and distinctly
through the telescope as if seen with the
ma ked eye at Il distance of Il, 500 miles. But
that is hardly the case. The magnifying
power of 1000 is one that can seldom be
used upon even the best and biggest tele-
scope, and perhaps it may be said il can
never be used to give the distnctness of
vision that theoretically belongs to it,
A Heavy Tax on CreduIity.
Instability of the instrument due to un-
in ho a. trnO m nl,era ll limo
on the earth are magnified just much as
the object looked at is magnified for which
reason a steady view with the highest mag
nifying power is seldom possible. But sup
posing it to be so u round disk half a yard IN
diameter, at distance of one mile, subtends
an angie OF nearly one minute of an arc,
which is not ar from the limit of distinct
ness for ordinary vision, SO that distance
of is, 900 miles would give a diameter of9,0O0
yards or not far from five miles for the
necessary diameter of a circular spot on the
breadth of a longer band that could be
studied with reasona Dle hope OF making out
anything concerning it.
Therefore it would seem that any signal
that might he made by the inhabitants OF
Mars would have to he nearly that size, and
the Likelihood of their constructing artificial
works of sucn magnitude may be said 10 be
rather q heavy tax upon the credullty OF
anybody who IS asked to believe it.
1t may be said that some of the Iynx-eyed
astronomers can make out objects of less
magnitude than stated, but supposing their
power of vision to be twice that of the Or
dinary man the smallest magnitude that can
be recognized will exceed two miles, and
.he difficulty Of dealing with it is diminished
rather in theory than in fact.
Ii it be difficulty. as explained, for the
people OF Mars to make anything big enough
TO be seen through the best telescopes, the
difficulties become much greater should the
people of the earth attempt to construct
signals that could.be seen by the inha bitanis
OF Mars. And for this reason: When the
earth is at its least distance from Mars it is
directly between that planet and the sun. 1t
is above the earth's horizon when the sun is
below, but at the same time the earth as
seen from Mars is SO close to tho sun as to be
invisible unless il happens to be directly be-