CHAPTER X
THE DISCOVERY OF LINES UPON MARS--THE GREAT MARTIAN CONTROVERSY
After the little interlude with M'Allister, I resumed my remarks bysaying that "The year 1877, so memorable for the near approach of Marsand the discovery of its two tiny satellites, was also the year in whicha still more important discovery was made--a discovery, in fact, whichhas much enlarged our knowledge of the planet, and has also resulted inan entire revision of our conceptions respecting it.
"An Italian astronomer, Signor Schiaparelli, took advantage of thefavourable position of Mars to observe it very carefully, and some timeafterwards announced that he had seen upon its surface a number of veryfine lines which had not previously been noticed, and these he hadcarefully charted upon his drawings and maps.
"This announcement started one of the most acrimonious discussions thatthe astronomical world has ever known; and although it is now overthirty years since it commenced, astronomers are still divided into twoparties--one accepting the lines as demonstrated facts, the other eitherdenying their existence, or endeavouring to explain them away by variousmore or less ingenious or fanciful theories.
_From a Globe made by M. Wicks_ Plate VIII
MARS. MAP I
In all these maps the south is at the top. The dark shaded portions arevegetation, mostly on old sea-beds. The fine lines are the canals, andthe round dots the oases. The light areas are deserts. Longitude "0" isseen on the Equator between the two forks of the "Sabaeus Sinus."]
"When Signor Schiaparelli's statements and drawings were firstdiscussed, it was declared by some to be quite impossible that thesefine lines could really have been seen by him: either his eyes must havebeen overstrained, or he claimed to see more than he actually did see.So warm did the discussion become that he soon withdrew from italtogether, but devoted himself to his work. As time went on, he notonly verified his previous discoveries, but found numerous fresh lines,all of which appeared to run straight and true over many hundreds ofmiles on the planet.
"Milan then had a good clear atmosphere which was favourable for theobservation of delicate planetary markings, and other observers who werewell situated were able to see and draw many of the lines whichSchiaparelli had discovered.
"It was, however, contended that such lines could not have any realexistence, as it was asserted that they were too straight. It is quitetrue that straight lines on a rotating globe would appear curved whenseen from some points of view, but if the objectors had carefullystudied complete sets of drawings, they would have seen that the linesdid assume a curved form in certain aspects of the planet.
"Then the very same people who denied the actuality of the lines becausethey were too straight, eagerly took up a suggestion that they were notactually narrow lines, but the edges of diffused shadings on the planet,apparently quite oblivious of the fact that the same objections mustapply to them. Moreover, if there was difficulty in accepting theactuality of narrow lines, there must be immensely greater difficulty inbelieving that shadings could, in such a very large number of cases, allend in straight lines many hundreds or thousands of miles long, andalways appear uniformly true, no matter upon what portion of the discthey might be seen, and whatever might be the angle of illumination.
"Besides, only a small proportion of the lines are connected withshadings. The shadings are more likely to be the result of the canalsthan the cause of the formation of illusory lines in so many cases.
"I have listened to many of these discussions, and have often been muchamused at the tangle of inconsistencies in which some have involvedthemselves, by taking up fresh theories without regard to their previouscontentions.
"As time went on each opposition of Mars brought the discovery of freshlines, and numerous observers confirmed the reality of Schiaparelli'swork.
"Professor Lowell, the well-known American astronomer, took up the studyof Mars in a most thorough and systematic manner, and has sincepractically made it his life's work. An observatory was built atFlagstaff, Arizona, far away from towns and smoke, at an altitude ofover 6000 feet above the sea-level, the site being specially selected onaccount of the clearness and purity of its atmosphere; while theobservatory, being high up above the denser and more disturbed strata ofair, afforded the most favourable situation possible for the properobservation 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, bylong-continued and most systematic work, added greatly to our knowledgeof Mars. Year after year has seen the addition of more lines on our mapsof the planet, whilst many interesting discoveries have been made--onebeing that some of the fine lines were double, the second line alwaysbeing equidistant from the first one throughout its whole length, nomatter whether the lines were straight or curved.
"This caused a further outcry of objection. The observers were told thatthey had been overstraining their eyesight so that they 'saw double,'and also that they had been using telescopes not properly focussed. Suchobjections seem almost beyond argument, for no practical observer coulduse an improperly focussed instrument without at once discovering thedefect.
"Besides, if the double lines were the result of eye-strain, or anyother defect which might cause such illusions, all the lines would havebeen 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 wereso seen, and it made no difference what position they occupied on thedisc, or at what angles they were presented. Some of the doubles were,in fact, curved lines; and another point was that in some cases theywere only doubled at certain seasons of the year.
"Other observers who saw the lines were charged with having studied themaps of Schiaparelli and Lowell until they had become obsessed with thelines, and when they looked through the telescope simply fancied theysaw them!
"In England our atmospheric conditions are seldom really favourable tothe proper seeing of the finer detail, and the very faint lines cannotbe seen at all. The lines that are visible do not appear thin and sharpas they do to observers in more favoured climes, but rather as diffusedsmudgy lines, and so they are drawn by the observers. On a fewoccasions of exceptionally good seeing they have, however, been seen anddrawn as finer and sharper lines.
"The visibility of the lines was, however, confirmed by so manyobservers of known integrity, and from so many different parts of theworld, that the objectors were at last compelled to abandon the positionthey had occupied. Then a new theory was started, viz. that the lineswere actually seen but did not actually exist, being really opticalillusions arising from the apparent integration, or running together inlinear form, of various small disconnected markings which were viewedfrom beyond the distance of clear seeing.
"The manner in which it was sought to prove the correctness of thistheory appeared to me at the time (and still does so) as most weak andfallacious, and certain experiments I made only strengthened thatopinion. However, scientific people accepted it as proof.
"In making this experiment schoolboys were seated in rows at differentmeasured distances from a map of Mars, which they were told to copy. Themap showed all the well-known dark patches and markings, but no finelines. About the places where some of those lines should have been,dots, curls, wisps, &c., were inserted at irregular distances, and notalways exactly where the lines should have been shown. The inevitableresult was that the boys who were too far away to see clearly saw thesesmall markings as continuous straight lines, and so drew them. In thecircumstances they could not do otherwise; for if sufficient marks wereinserted nearly in alignment, they would necessarily produce the effectof lines.
"These drawings were then acclaimed as _proving_ that the lines seen onMars were only discrete markings viewed from beyond the distance ofclear seeing, and that the network of lines seen and drawn by so manyskilled and careful observers of Mars had no actual existence upon theplanet. Thus all their work was completely discredited.
"
Experiments like these could not possibly prove any such thing, becauseit would be easy to insert in a map various markings which, when viewedfrom a distance, would appear to form almost any design that one mightchoose to depict. Any desired effect might thus be obtained; and I haveseen many pictures so formed in which the illusion was perfect. Whenviewed from a distance each appeared to be a picture of somethingentirely different from what was seen when it was viewed from a nearstandpoint.
"The linear illusion could not arise from a mere multiplicity of faintscattered markings, but all the more conspicuous markings must be inalignment. It seems impossible to imagine that so many hundreds of lineson Mars could thus fortuitously be formed by illusion, and _every_ linebe connected to some definite point at each end.
"To argue that because illusory lines can be formed as in theseexperiments proves that the Martian lines are also illusions is claimingfar too much. For instance, if I drew what was actually a map of SouthAfrica, and was so seen at close quarters, yet in consequence of theinsertion of numerous small marks and shadings formed a portrait of LordBlank when viewed from a distance, it would be very far indeed fromproving 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 theyhad not even drawn correctly the outlines of the dark patches aboutwhich there was no dispute.
"It is obvious that such erroneous and unreliable work as this could notbe regarded as evidence upon which truly scientific argument could befounded for the purpose of deciding such a contentious question; yetmainly upon this very slender and unreliable evidence meetings of two ofour leading astronomical associations endorsed the illusion theory, andfor a long time it held the field.
"M. Flammarion made some similar experiments in Paris, and even insertedspaced 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 toosparing with his dots and marks.
"A long series of experiments was carefully carried out by ProfessorLowell and his colleagues, from which it was deduced that if in any lineon Mars there was a gap of sixteen miles in length, our presenttelescopes would suffice to discover it. It is most improbable that inso many hundreds of lines, several of which are over two thousand milesin length, there would not be numerous gaps over sixteen miles long ifthe lines were made up of separate markings.
"Yet it is found that every line is perfect in its continuity, and notonly so, but uniform in width throughout its whole length, which wouldbe impossible if the lines were made up of separate markings not inalignment.
"The illusion theory may, however, to a certain extent be correct, butthis will prove exactly the opposite of what its supporters contend. Itappears to have been quite overlooked that as there are so manythousands of miles of canals it is utterly impossible to suppose thatthe vegetation, which is all that we really see, is continuous andwithout breaks. It would indeed be most extraordinary if there were notvery many long stretches of land which, for some natural or utilitarianreasons, were either bare of vegetation or so sparsely covered as toappear bare when viewed from the earth through a telescope. Some partsof the canals in hilly or rocky ground may pass through tunnels, andthus cause apparent gaps in the lines; or ground may be incapable ofbearing vegetation, or purposely left fallow.
"It would, therefore, be no matter of surprise if more powerfulinstruments should, in moments of perfect seeing, reveal numerousapparent gaps in the lines. So far from proving they were not canals,such gaps are exactly what we should expect to find in connection withcanals; and the lines would probably appear as irregular light and darkpatches in alignment, because we do not see the canals themselves, butonly the vegetation on the land which they traverse. Probably there arealso many oases yet to be discovered along the canal lines.
"As I have already stated, it was asserted that the double lines wereillusions arising from the causes already mentioned, with the probableaddition of eye-strain and bad focussing. Assuming that the single linesare, as it is declared, illusions, we are confronted with theassumption that the doubles are illusions of illusions, and this is morethan I can follow, it seems so improbable.
"Professor Lowell has devoted some sixteen years to close and continuousobservation of Mars whenever it has been in a position to be observed,and many thousands of drawings have been made, the results being plotteddown on a globe. In reply to the statements of occasional observers thatthe lines cannot be seen, he testifies that they are not difficult tosee; and that any one who saw them in his exceptionally good atmosphere,and through his instruments, could have no doubt of their actuality. Herather caustically, but very justly, remarks in one of his books thathis many years of personal experience in viewing these lines almostentitle him to an opinion on the subject equal to those who have hadnone at all!
"The proof of their existence, however, no longer rests only on thecorroborative evidence of other observers, for, after years ofexperiment, Professor Lowell and his staff have succeeded in takingdirect photographs of Mars, which show several of the disputed lines.One would have thought that would settle the question, but, althoughsome of the more reasonable of the objectors have been convinced by theevidence of the photographs, many others still maintain their attitudeof scepticism, especially those who have not themselves seen thephotographs. They declare it to be quite impossible for any suchphotographs to be taken, because our atmosphere would prevent anyphotographic definition of fine detail on such small pictures; yet aboutten thousand of these tiny photographs were taken during the nearapproach of Mars in 1907.
"As I possess a number of these photographs I can testify that they doshow some of the lines, and persons who disbelieved have expressedsurprise at their excellence. Success was only obtained by means ofspecially sensitised plates, for the ordinary photographic rays andordinary plates were found useless, whilst the process of photographingso small and distant a planet is surrounded with difficulties.
"Even when attached to a telescope giving an equivalent focal length ofnearly 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 wereused on the telescope to obtain a larger image, then its light must bestill fainter, and thus a longer exposure would be required to obtain apicture on the plate. As Mars moves in its orbit and rotates on itsaxis, and our atmosphere is subject to continual movement anddisturbance, any long exposure would result in a blurred picture, whichwould show no fine detail. So, as a short exposure is essential, only asmall picture can be taken. Nothing is gained by any subsequent greatenlargement of the picture, because the grain of the film of a quickplate is coarse; and, if enlarged, this also blurs out the detail.
"Having regard to all the difficulties which had to be surmounted, itwas a great and undoubted triumph to secure detail on such tinyphotographs of this distant world. As time goes on improvements willprobably be effected and still better pictures secured; but enough hasnow been accomplished to prove that the lines cannot be illusions, butreally exist upon the planet. If the eye can be deceived in thisrespect, the camera cannot.
"When Professor Lowell first took up the work of Martian observationonly 113 lines had been discovered by Schiaparelli, but the number hasgradually been added to from time to time, as the result of the workdone at Flagstaff Observatory and elsewhere, and has now reached a totalof considerably more than 600, the lines forming a fine networkextending all over the planet.
"Mr. Slipher, who accompanied Professor Todd's expedition to Alianza inChili, at the opposition of 1907, together with the observers atFlagstaff, discovered no less than 85 new canals, including somedoubles, nearly all being in the more southern portions of the southernhemisphere.
"In addition to the discovery of so many fine lines, we also owe to theacumen of Professor Lowell a reasonable explanation of what they reallyare. Schiaparelli termed them 'canali,' an Italian term for 'channels,'but, popularly, th
is soon became corrupted into the term 'canals,' andthis has turned out to be a much more appropriate word than suchcorruptions usually are.
_From a Globe made by M. Wicks_ Plate IX
MARS. MAP II
The Solis Lacus is seen as an oval patch near the top, and many longcanals, some double, are shown. A very large proportion of the area onthis map is desert land.]