ear 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
alignment.

"The illusion theory may, however, to a certain extent be correct, but
this will pro