The Discovery Of Lines Upon Mars-the Great Martian Controversy
From: To Mars Via The Moon
After the little interlude with M'Allister, I resumed my remarks by
saying that "The year 1877, so memorable for the near approach of Mars
and the discovery of its two tiny satellites, was also the year in which
a still more important discovery was made-a discovery, in fact, which
has much enlarged our knowledge of the planet, and has also resulted in
an entire revision of our conceptions respecting it.
"An Italian astronomer, Signor Schiaparelli, took advantage of the
favourable position of Mars to observe it very carefully, and some time
afterwards announced that he had seen upon its surface a number of very
fine lines which had not previously been noticed, and these he had
carefully charted upon his drawings and maps.
"This announcement started one of the most acrimonious discussions that
the astronomical world has ever known; and although it is now over
thirty years since it commenced, astronomers are still divided into two
parties-one accepting the lines as demonstrated facts, the other either
denying their existence, or endeavouring to explain them away by various
more or less ingenious or fanciful theories.
MARS. MAP I
In all these maps the south is at the top. The dark shaded portions are
vegetation, mostly on old sea-beds. The fine lines are the canals, and
the round dots the oases. The light areas are deserts. Longitude "0" is
seen on the Equator between the two forks of the "Sabaeus Sinus."]
"When Signor Schiaparelli's statements and drawings were first
discussed, it was declared by some to be quite impossible that these
fine lines could really have been seen by him: either his eyes must have
been overstrained, or he claimed to see more than he actually did see.
So warm did the discussion become that he soon withdrew from it
altogether, but devoted himself to his work. As time went on, he not
only verified his previous discoveries, but found numerous fresh lines,
all of which appeared to run straight and true over many hundreds of
miles on the planet.
"Milan then had a good clear atmosphere which was favourable for the
observation of delicate planetary markings, and other observers who were
well situated were able to see and draw many of the lines which
Schiaparelli had discovered.
"It was, however, contended that such lines could not have any real
existence, as it was asserted that they were too straight. It is quite
true that straight lines on a rotating globe would appear curved when
seen from some points of view, but if the objectors had carefully
studied complete sets of drawings, they would have seen that the lines
did assume a curved form in certain aspects of the planet.
"Then the very same people who denied the actuality of the lines because
they were too straight, eagerly took up a suggestion that they were not
actually narrow lines, but the edges of diffused shadings on the planet,
apparently quite oblivious of the fact that the same objections must
apply to them. Moreover, if there was difficulty in accepting the
actuality of narrow lines, there must be immensely greater difficulty in
believing that shadings could, in such a very large number of cases, all
end in straight lines many hundreds or thousands of miles long, and
always appear uniformly true, no matter upon what portion of the disc
they might be seen, and whatever might be the angle of illumination.
"Besides, only a small proportion of the lines are connected with
shadings. The shadings are more likely to be the result of the canals
than the cause of the formation of illusory lines in so many cases.
"I have listened to many of these discussions, and have often been much
amused at the tangle of inconsistencies in which some have involved
themselves, by taking up fresh theories without regard to their previous
"As time went on each opposition of Mars brought the discovery of fresh
lines, and numerous observers confirmed the reality of Schiaparelli's
"Professor Lowell, the well-known American astronomer, took up the study
of Mars in a most thorough and systematic manner, and has since
practically made it his life's work. An observatory was built at
Flagstaff, Arizona, far away from towns and smoke, at an altitude of
over 6000 feet above the sea-level, the site being specially selected on
account of the clearness and purity of its atmosphere; while the
observatory, being high up above the denser and more disturbed strata of
air, afforded the most favourable situation possible for the proper
observation of delicate planetary detail.
"There he continued the work which Schiaparelli had commenced, and,
together with the colleagues with whom he has been associated, has, by
long-continued and most systematic work, added greatly to our knowledge
of Mars. Year after year has seen the addition of more lines on our maps
of the planet, whilst many interesting discoveries have been made-one
being that some of the fine lines were double, the second line always
being equidistant from the first one throughout its whole length, no
matter whether the lines were straight or curved.
"This caused a further outcry of objection. The observers were told that
they had been overstraining their eyesight so that they 'saw double,'
and also that they had been using telescopes not properly focussed. Such
objections seem almost beyond argument, for no practical observer could
use an improperly focussed instrument without at once discovering the
"Besides, if the double lines were the result of eye-strain, or any
other defect which might cause such illusions, all the lines would have
been seen double, or at least all the lines running at the same angles;
but as a matter of fact only a very small proportion of the lines were
so seen, and it made no difference what position they occupied on the
disc, or at what angles they were presented. Some of the doubles were,
in fact, curved lines; and another point was that in some cases they
were only doubled at certain seasons of the year.
"Other observers who saw the lines were charged with having studied the
maps of Schiaparelli and Lowell until they had become obsessed with the
lines, and when they looked through the telescope simply fancied they
"In England our atmospheric conditions are seldom really favourable to
the proper seeing of the finer detail, and the very faint lines cannot
be seen at all. The lines that are visible do not appear thin and sharp
as they do to observers in more favoured climes, but rather as diffused
smudgy lines, and so they are drawn by the observers. On a few
occasions of exceptionally good seeing they have, however, been seen and
drawn as finer and sharper lines.
"The visibility of the lines was, however, confirmed by so many
observers of known integrity, and from so many different parts of the
world, that the objectors were at last compelled to abandon the position
they had occupied. Then a new theory was started, viz. that the lines
were actually seen but did not actually exist, being really optical
illusions arising from the apparent integration, or running together in
linear form, of various small disconnected markings which were viewed
from beyond the distance of clear seeing.
"The manner in which it was sought to prove the correctness of this
theory appeared to me at the time (and still does so) as most weak and
fallacious, and certain experiments I made only strengthened that
opinion. However, scientific people accepted it as proof.
"In making this experiment schoolboys were seated in rows at different
measured distances from a map of Mars, which they were told to copy. The
map showed all the well-known dark patches and markings, but no fine
lines. About the places where some of those lines should have been,
dots, curls, wisps, &c., were inserted at irregular distances, and not
always exactly where the lines should have been shown. The inevitable
result was that the boys who were too far away to see clearly saw these
small markings as continuous straight lines, and so drew them. In the
circumstances they could not do otherwise; for if sufficient marks were
inserted nearly in alignment, they would necessarily produce the effect
"These drawings were then acclaimed as proving that the lines seen on
Mars were only discrete markings viewed from beyond the distance of
clear seeing, and that the network of lines seen and drawn by so many
skilled and careful observers of Mars had no actual existence upon the
planet. Thus all their work was completely discredited.
"Experiments like these could not possibly prove any such thing, because
it would be easy to insert in a map various markings which, when viewed
from a distance, would appear to form almost any design that one might
choose to depict. Any desired effect might thus be obtained; and I have
seen many pictures so formed in which the illusion was perfect. When
viewed from a distance each appeared to be a picture of something
entirely different from what was seen when it was viewed from a near
"The linear illusion could not arise from a mere multiplicity of faint
scattered markings, but all the more conspicuous markings must be in
alignment. It seems impossible to imagine that so many hundreds of lines
on Mars could thus fortuitously be formed by illusion, and every line
be connected to some definite point at each end.
"To argue that because illusory lines can be formed as in these
experiments proves that the Martian lines are also illusions is claiming
far too much. For instance, if I drew what was actually a map of South
Africa, and was so seen at close quarters, yet in consequence of the
insertion of numerous small marks and shadings formed a portrait of Lord
Blank when viewed from a distance, it would be very far indeed from
proving that every map of South Africa was a portrait of the noble lord,
or that his portraits were all maps of South Africa.
"Moreover, as I myself saw, some of the boys were so unskilled that they
had not even drawn correctly the outlines of the dark patches about
which there was no dispute.
"It is obvious that such erroneous and unreliable work as this could not
be regarded as evidence upon which truly scientific argument could be
founded for the purpose of deciding such a contentious question; yet
mainly upon this very slender and unreliable evidence meetings of two of
our leading astronomical associations endorsed the illusion theory, and
for a long time it held the field.
"M. Flammarion made some similar experiments in Paris, and even inserted
spaced dots along the sites of canal lines on the map put up as a copy,
yet not one boy drew a canal. M. Flammarion evidently was rather too
sparing with his dots and marks.
"A long series of experiments was carefully carried out by Professor
Lowell and his colleagues, from which it was deduced that if in any line
on Mars there was a gap of sixteen miles in length, our present
telescopes would suffice to discover it. It is most improbable that in
so many hundreds of lines, several of which are over two thousand miles
in length, there would not be numerous gaps over sixteen miles long if
the lines were made up of separate markings.
"Yet it is found that every line is perfect in its continuity, and not
only so, but uniform in width throughout its whole length, which would
be impossible if the lines were made up of separate markings not in
"The illusion theory may, however, to a certain extent be correct, but
this will prove exactly the opposite of what its supporters contend. It
appears to have been quite overlooked that as there are so many
thousands of miles of canals it is utterly impossible to suppose that
the vegetation, which is all that we really see, is continuous and
without breaks. It would indeed be most extraordinary if there were not
very many long stretches of land which, for some natural or utilitarian
reasons, were either bare of vegetation or so sparsely covered as to
appear bare when viewed from the earth through a telescope. Some parts
of the canals in hilly or rocky ground may pass through tunnels, and
thus cause apparent gaps in the lines; or ground may be incapable of
bearing vegetation, or purposely left fallow.
"It would, therefore, be no matter of surprise if more powerful
instruments should, in moments of perfect seeing, reveal numerous
apparent gaps in the lines. So far from proving they were not canals,
such gaps are exactly what we should expect to find in connection with
canals; and the lines would probably appear as irregular light and dark
patches in alignment, because we do not see the canals themselves, but
only the vegetation on the land which they traverse. Probably there are
also many oases yet to be discovered along the canal lines.
"As I have already stated, it was asserted that the double lines were
illusions arising from the causes already mentioned, with the probable
addition of eye-strain and bad focussing. Assuming that the single lines
are, as it is declared, illusions, we are confronted with the
assumption that the doubles are illusions of illusions, and this is more
than I can follow, it seems so improbable.
"Professor Lowell has devoted some sixteen years to close and continuous
observation of Mars whenever it has been in a position to be observed,
and many thousands of drawings have been made, the results being plotted
down on a globe. In reply to the statements of occasional observers that
the lines cannot be seen, he testifies that they are not difficult to
see; and that any one who saw them in his exceptionally good atmosphere,
and through his instruments, could have no doubt of their actuality. He
rather caustically, but very justly, remarks in one of his books that
his many years of personal experience in viewing these lines almost
entitle him to an opinion on the subject equal to those who have had
none at all!
"The proof of their existence, however, no longer rests only on the
corroborative evidence of other observers, for, after years of
experiment, Professor Lowell and his staff have succeeded in taking
direct photographs of Mars, which show several of the disputed lines.
One would have thought that would settle the question, but, although
some of the more reasonable of the objectors have been convinced by the
evidence of the photographs, many others still maintain their attitude
of scepticism, especially those who have not themselves seen the
photographs. They declare it to be quite impossible for any such
photographs to be taken, because our atmosphere would prevent any
photographic definition of fine detail on such small pictures; yet about
ten thousand of these tiny photographs were taken during the near
approach of Mars in 1907.
"As I possess a number of these photographs I can testify that they do
show some of the lines, and persons who disbelieved have expressed
surprise at their excellence. Success was only obtained by means of
specially sensitised plates, for the ordinary photographic rays and
ordinary plates were found useless, whilst the process of photographing
so small and distant a planet is surrounded with difficulties.
"Even when attached to a telescope giving an equivalent focal length of
nearly 150 feet, the camera only gives a very tiny image of the planet.
The lighting of the small image is faint, but if additional power were
used on the telescope to obtain a larger image, then its light must be
still fainter, and thus a longer exposure would be required to obtain a
picture on the plate. As Mars moves in its orbit and rotates on its
axis, and our atmosphere is subject to continual movement and
disturbance, any long exposure would result in a blurred picture, which
would show no fine detail. So, as a short exposure is essential, only a
small picture can be taken. Nothing is gained by any subsequent great
enlargement of the picture, because the grain of the film of a quick
plate is coarse; and, if enlarged, this also blurs out the detail.
"Having regard to all the difficulties which had to be surmounted, it
was a great and undoubted triumph to secure detail on such tiny
photographs of this distant world. As time goes on improvements will
probably be effected and still better pictures secured; but enough has
now been accomplished to prove that the lines cannot be illusions, but
really exist upon the planet. If the eye can be deceived in this
respect, the camera cannot.
"When Professor Lowell first took up the work of Martian observation
only 113 lines had been discovered by Schiaparelli, but the number has
gradually been added to from time to time, as the result of the work
done at Flagstaff Observatory and elsewhere, and has now reached a total
of considerably more than 600, the lines forming a fine network
extending all over the planet.
"Mr. Slipher, who accompanied Professor Todd's expedition to Alianza in
Chili, at the opposition of 1907, together with the observers at
Flagstaff, discovered no less than 85 new canals, including some
doubles, nearly all being in the more southern portions of the southern
"In addition to the discovery of so many fine lines, we also owe to the
acumen of Professor Lowell a reasonable explanation of what they really
are. Schiaparelli termed them 'canali,' an Italian term for 'channels,'
but, popularly, this soon became corrupted into the term 'canals,' and
this has turned out to be a much more appropriate word than such
corruptions usually are.
MARS. MAP II
The Solis Lacus is seen as an oval patch near the top, and many long
canals, some double, are shown. A very large proportion of the area on
this map is desert land.]
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