of Oxford, does not regard the various contributions on the surface
features of Mars as belonging to astronomical science may be inferred
from his interesting book lately published, entitled "Astronomical
Discovery." This book presents to us the history of the discovery of
Uranus and Eros, of Neptune, Bradley's aberration of light, Schwabe and
sun-spot period, the variation of latitude, etc., but not a word about
the marvellous discoveries of the _canali_ of Mars by Schiaparelli, so
fully confirmed by the observation and drawings of many others, and the
great advances made by Lowell in the discovery of new features with his
lucid and rational interpretation of the seeming enigmas.
Astronomy, the oldest and most conservative of all the sciences, has
been the last to subdivide. Already one group of men has justified
by its work a division of the science known as astrophysics. The
lamented Keeler, in explaining the difference between astronomy and
astrophysics, said: "Astrophysics seeks to ascertain the nature of the
heavenly bodies, rather than their positions and motions in space,
_what_ they are, rather than _where_ they are." This natural division
suggests the propriety of making another division equally distinct,
which should comprise the study and interpretation of the surface
markings of the planets and satellites, under the name of planetology.
The study would be the application to these bodies of the science
of geology, in its broadest sense, meteorology, physical geography,
geodesy, and related sciences.
With the science of planetology established, the student of this
science will no longer call to his aid the astronomer, and, least of
all, the astrophysicist, nor will he be mindful of their criticism or
neglect. He will appeal to the sciences which are involved in the study
of the surface features of his own globe, in the interpretation of
planetary detail.
VII
DIFFICULTIES OF SEEING
_It is contrary to all the analogies of nature to suppose
that life began only on a single world._
SIMON NEWCOMB.
For years I had been familiar with different representations of Mars
in which the surface features had been strongly depicted in black and
white; in other words, photo-reliefs, or engravings incorporated with
the printed page. I had unwittingly come to believe that these features
were equally distinct when one observed Mars through the telescope. I
had not then seen Schiaparelli's original memoir in which his wonderful
map presents the canals in light and tenuous lines, which are, however,
as clear cut as the lines of a steel engraving, to use his words. For
a long time I had hoped for a chance to observe Mars through a large
telescope in a clear and steady atmosphere. It seemed reasonable to
me--knowing nothing about it--that one who had traced out under the
microscope delicate lines and structural features in diaphanous
membranes, who had, in fact, used a microscope with high powers for
forty years, would find it child's play to make out the canals, oases,
regions, etc., of Mars, as represented in the various publications on
the subject. Professor Percival Lowell, of Flagstaff, Arizona, finally
gave me the opportunity I so much desired, and, through his courtesy
and kindness, I was enabled to observe Mars every night for nearly six
weeks through his twenty-four inch refractor, the last and probably
the best telescope ever made by Clark, mounted in one of the steadiest
atmospheres in the world and at an altitude above sea-level of over
7,000 feet. Imagine my surprise and chagrin when I first saw the
beautiful disk of Mars through this superb telescope. Not a line! not a
marking! The object I saw could only be compared in appearance to the
open mouth of a crucible filled with molten gold. Slight discolorations
here and there and evanescent areas outlined for the tenth of a second,
but not a determinate line or spot to be seen. Had I stopped that
night, or even a week later, I might have joined the ranks of certain
observers and said "illusion" or something worse. And right here it
was that my experience in microscopic work helped me, for, remembering
the hours--nay, days--I had worked, in making out structural features
in delicate organisms which my unprofessional friends could not see at
all, I realized that patient observation would be required if I was to
be successful in my efforts. My despair, however, was overwhelming when
Professor Lowell and his assistants, looking for a few moments at the
same object, would draw on paper the features which had been plainly
revealed to them, consisting of definite shaded regions, a number of
canals and other markings, of which, with the utmost scrutiny, I could
hardly detect a trace. For the first time I realized that observing
fixed diaphanous membranes under a microscope with rigid stand, and
within four inches of one's nose, was quite a different matter from
observing a brilliant disk 4,200 miles in diameter, 52,000,000 miles
away, with an oscillating atmosphere of unknown depth between. Night
after night I examined this golden, opalescent disk, drawing each
time such features as I could convey by memory from the ocular to the
drawing table, and, little by little, new features were detected, and
to my delight the drawings agreed with those made by the others. Since
the drawings made by the four observers coincided, it was evident that
we had not been victims of subjective phenomena. Furthermore, as I
discovered afterwards, by comparison, the drawings I made not only
agreed with theirs but with those made by other observers, at different
times, in other parts of the world. So slow were my acquisitions,
however, that it soon became evident that at least months of continuous
observation would be necessary before the more delicate markings would
be revealed to me. It is interesting to learn that others have had a
similar experience. Mr. A. Stanley Williams, of England, in an article
entitled "Notes on Mars" ("Observatory," June, 1899), in stating the
difficulties of observation, says: "My eye invariably requires at least
two months of continuous observation of a planet before it acquires its
full sensitiveness to the most minute details."
In this connection it is well to state that Mr. Lowell began the
observation of Mars when he was a mere boy. His first telescope, which
he still has, was a two and a quarter inch refractor. His observations
were made from the roof of his house in Boston, and with this small
glass he defined the general shaded regions that Huyghens had detected
and drawn in 1659. Since then Mr. Lowell has observed in turn through
a six inch, an eighteen inch of Brashear, and, for the last few years,
through a twenty-four inch refractor made by Clark especially for this
work.
To refute the accumulated observations of Mr. Lowell one must have the
same acute eye, and a record of the same continuous and devoted study.
Nothing short of that experience will avail. The jealous derision that
has gone up from some observers endowed with less acuteness of vision
is neither dignified nor just. Were these Martian details based upon
the observations of Lowell alone, one might be inclined to say that
some vagary of the mind had led him to imagine these markings which
were first detected by the great Italian astronomer Schiaparelli. Up
to the present time--to mention only a few--observations and drawings
have been made by Perrotin, Thollon, and Flammarion, of France; Dr.
Phil. Fauth, of Germany; Williams, of England; Lowell, W. H. Pickering,
Douglass, Lampland, and Schaeberle, of America, while many others have
made drawings of the more conspicuous details. With this record it is
impossible to deny the existence of these markings essentially as they
are drawn.
The difficulty of seeing the more delicate markings of the planet
is unquestionable, and an examination of astronomical literature,
from which we shall make numerous quotations, indicates only too
plainly the acuteness of vision, and the time and care necessary to
make competent observations. Sir Robert Ball says, in one of his
recent works: "The detection of the Martian features indicates one
of the utmost refinements of astronomical observations." Macpherson,
in his "Astronomers of To-day," thus writes of Schiaparelli,
"Professor Schiaparelli's observations have been distinguished by his
keen-sightedness and care. He has taken every precaution to avoid all
disturbances resulting from personal equation, and has found it well
to adopt the rule (which he here quotes) 'to abstain from everything
which could affect the nervous system, from narcotics and alcohol, and
especially from the abuse of coffee, which I found to be exceedingly
prejudicial to the accuracy of observation.'" What I might have
accomplished in the way of seeing had I followed the wise example of
Schiaparelli I do not know. A not too strict abstemiousness in any of
these matters, coupled with long daily walks on the Mesa, with its
fascinating flora and fauna, found me in the observer's chair every
night, somewhat fatigued mentally and physically.
Sir Robert Ball, in his "Popular Guide to the Heavens," in describing
the difficulty in making out the more delicate markings of Mars,
says: "It should be understood that in the unsteady air of England it
is almost hopeless to expect many of the finer details; not even in
the most favorable climates are they to be seen always, or all at
once, and much training of the eye is required before it is fit to
decide for or against the existence of these details on the verge of
invisibility." As another illustration, perhaps, of the difficulties
of seeing, Sir Robert, in the same book, says: "Observers of Mars are
divided into two camps, those who see the canals, and those who do not.
The former are in the strong position that they are perfectly sure that
they see what they represent in their drawings."
From the foregoing it must be evident that not only are the finer
markings on Mars most difficult to see even under the best conditions
but that exceptional acuteness of vision, which few possess, united
with long practice, is necessary to make out the tenuous lines which
enclose the field of Mars like a net. That Mr. Lowell has had a long
and continuous practice, covering years, in observing Mars through
the steadiest of atmospheres and with a superb glass, is simply a
statement of fact. It may be said without fear of contradiction that
he has devoted more time to the observation of Mars than all the other
observers combined. Has he then an exceptional acuteness of sight,
coupled with indefatigable industry, in the pursuit of this quest to
which he is devoting his life and fortune? The following instance
will illustrate his marvellous eyesight. We were walking along the
shores of a lake some miles from Flagstaff, the expanse of shore left
by the rapidly evaporating waters abounding with thousands of very
small black spiders running hither and thither at our approach. I
told him of one I had just seen in which the abdomen was covered with
minute young spiders which the mother was carrying about with her--a
well-known habit of certain species. This curious fact I had detected
only while stooping close to the ground in search of minute shells. Mr.
Lowell, while walking along, immediately began scanning the ground for
the trace of a spider with minutely granulated abdomen, and finally
exclaimed: "There is one of them!" On stooping down to examine the
object it proved to my astonishment to be a female carrying its young
in the way already described. This incident revealed a remarkable
acuteness of vision to detect, while standing erect and walking,
this tiny spider among hundreds of others of its species that were
scampering away at our approach.
Not only is acuteness of vision necessary to one who is to study
planetary markings, but of importance also is a clear, and above all
a steady atmosphere; and, strange as it may appear, telescopes of
moderate size seem to be the instruments with which the best work has
been done. It is also true in astronomy, as in warfare, that it is not
the biggest gun but the man behind the gun that does the most efficient
work. As an evidence of the importance of steady atmosphere Professor
W. H. Pickering, in his observations on the satellites of Jupiter,
says his work had two important bearings: "First, as showing the
relative importance of atmosphere _versus_ aperture for delicate visual
observations of this sort. In the same category would be included
studies of planetary detail as distinguished from the examination of
very faint objects. In other words, if an observer wishes to study
very faint stars he must have a large telescope. If he wishes to study
the neighboring planets and brighter satellites he may use a small
telescope, but he must have a very good atmosphere."
The importance of a clear and steady atmosphere, for delicate
observation, is known to all astronomers. The rarity of such days,
even in our clear atmosphere so superior to that of England, is not
generally known. Forty years ago Dr. Henry Draper, in an address
entitled "Are Other Worlds Inhabited?" in speaking of Mars and the
difficulties of seeing, said: "One of the greatest obstacles to
distinct vision is our own atmosphere. Its currents and motions tend
to confuse the outlines of objects, and, according to my experience, a
whole year may pass without the occurrence of more than one good night.
The only remedy is to carry the telescope as high up on a mountain
as possible, so as to leave below the more injurious portions of the
atmosphere. It might be possible to work 15,000 feet above the sea in
the neighborhood of the Equator." I quote these words that the general
reader may appreciate the advantages Lowell has with his fine telescope
south of all European observatories, in the latitude, say of Algiers,
at a high altitude, and in the dry and steady atmosphere of Arizona,
with uninterrupted seeing for weeks together, and each night far
superior to any night which Greenwich could ever be blessed with.
Professor W. H. Pickering attests to the importance of a steady
atmosphere in studying the Moon from a station in Jamaica, when he
says that, with a five inch refractor, he was able to detect minute
details which were not revealed by the far larger telescopes at Harvard
University.
Mr. W. D. Barbour, President of the Leeds Astronomical Society, using
his four inch achromatic, says: "In one of those brief intervals
of atmospheric steadiness I saw distinctly a number of well-known
markings," the names of which he gives. Dr. Phil. Fauth, using a seven
inch refractor, made sixty-three drawings of Mars, showing in wonderful
detail the canals, oases, etc. Mr. W. J. Lockyer, in London "Nature,"
testifies that "a keen and patient observer, sitting at the eyepiece of
a comparatively small equatorially mounted telescope, if he makes his
observations carefully, and with due regard to atmospheric conditions
for good seeing, can do more useful and valuable work than one who has
a large aperture at his command and employs it indifferently." Mr. E.
Ledger, in speaking of Dawes, who made a remarkable map of Mars, says
he was justly famed for the remarkable distinctness of his vision; he
had detected and drawn a few lines which seemed to be identical to
those of Schiaparelli.
In the authorities above quoted we have endeavored to show that a
steady atmosphere, a persistent devotion to the work, accompanied by
acute vision, and also a talent for observation, are all the factors
needed, not only to confirm the remarkable discoveries of Schiaparelli
and Lowell, but possibly to detect, at favorable moments, new features
which have escaped the eyes of these keen observers.
At this point we cannot resist giving the words of Sir David Gill,
Director of the Royal Observatory at the Cape of Good Hope. Professor
S. W. Burnham, of the Lick Observatory, in reviewing a memoir entitled
"Double Star Observations at the Cape of Good Hope," quotes as
follows from the preface: "Sir David Gill, in speaking of the routine
character of the work involved in the investigation, says: 'There is
no instance, as far as I know, of a long and valuable series of double
star discovery and observation made by a mere assistant acting under
orders. _It is a special faculty, an inborn capacity, a delight in the
exercise of exceptional acuteness of eyesight and natural dexterity,
coupled with the gift of imagination as to the true meaning of what he
observes, that imparts to the observer the requisite enthusiasm for
double star observing._ No amount of training or direction could have
created the Struves, a Dawes, or a Dembowski. _The great double star
observer is born, not made_, and I believe that no extensive series of
double star measurement will ever emanate from a regular observatory,
through successive directorates, unless men are specially selected
who have previously distinguished themselves in that field of work,
and who were originally driven to it from sheer compulsion of inborn
taste.'" If the reader will substitute the words _planetary markings_
for _double star_ in the above quotation from Sir David Gill's report,
he will understand why we have ventured to italicise certain lines, and
will appreciate their significance. In no stronger or truer words could
one have emphasized the conditions involved in a critical study of the
surface features of Mars.
In the experience of an astronomer, it is not an unusual occurrence
that an object in the heavens, fairly conspicuous, remains unseen
until by some lucky chance an observer sweeping the sky picks it
up, and, having determined its position, it is promptly found by
others. Professor H. H. Turner, in his "Astronomical Discovery of the
Nineteenth Century," says: "It is a common experience in astronomy that
an observer may fail to notice in a general scrutiny, some phenomenon
which he can see perfectly well when his attention is called to it;
when a man has made a discovery, and others are told what to look for,
they often see it so easily that they are filled with amazement and
chagrin that they never saw it before."
In the Rev. T. W. Webb's interesting book on "Celestial Objects for
Common Telescopes," a reminiscence of the author is given by a friend
in which the following is related as illustrating the varying ability
of observers in seeing. "A curious instance of difference of vision was
well illustrated one superb evening when Mr. Webb and the writer were
observing Saturn with the nine and a half inch refractor at Hardwick.
Mr. Webb saw distinctly the division in the outer ring which the writer
could not see a trace of, while the writer picked up a faint point of
light which afterwards turned out to be Enceladus (a satellite) which
Mr. Webb could not see."
In my brief observation of Mars I probably might have made out many
more details if I had permitted Mr. Lowell to tell me what to see, and
where to look for them on the disk. This I would not allow him to do,
nor did I study any of the numerous drawings in his own work, or the
original memoirs of Schiaparelli, or other works containing drawings of
Mars in his library. I would not learn the names of any of the regions,
or canals, nor with a single exception do I know them now. Only when
I had finished my last night's observations, did Mr. Lowell take my
drawings and write out a list of the various canals, oases, etc., which
I had made out. Thus, unaided, I drew simply what was plainly evident,
though many other details flashed out for a second, which were not
recorded, simply because I did not see them often enough to be sure of
their precise position on the disk.
Mr. Lowell points out one of the reasons why so many observers and
astronomers have not seen the canals. In the third volume of the
"Annals of the Lowell Observatory" he refers to a certain series of
observations of Mars, made in 1894, and says: "Not only was there
no sign of a canal, but even the main markings showed disheartingly
indefinite." "This vacancy of expression was due to the Martian date."
"It was the very nick of time to see nothing, for the part of the
planet most presented to the Earth was then at the height of the dead
season, and in this fact lies the key to much past undetection and
present unbelief in the phenomenon of the canals."
VIII
VARIATION IN DRAWING
_Let us not cheat ourselves with words. Conservatism sounds
finely and covers any amount of ignorance and fear._
PERCIVAL LOWELL.
Much doubt has been expressed as to the existence of the so-called
canals in Mars and other surface markings of that planet in consequence
of the discrepancy seen in the drawings of the more delicate features
by various observers. While in the main a certain general resemblance
is seen in the topographical character of the network of lines,
and a more close resemblance in the darker markings, notably the
Syrtis Major, the disagreement in the minor details has led certain
astronomers to deny their existence altogether, or to insist that most
of the markings were subjective, or due to poor focusing, or the result
of aberration of the eye or lens. Professor Simon Newcomb, in his "New
Astronomy for Everybody," in speaking of the work of the observers at
the Lick Observatory and the great telescope at their command coupled
with favorable situation, says: "It is therefore noteworthy that the
markings on the face of Mars as presented by Barnard do not quite
correspond to the channels of Schiaparelli and Lowell." Newcomb also
reproduces in his book the drawings of a region in Mars known as Solis
Lacus, made by Campbell and Hussey, and finds they do not show an exact
agreement between them. Now such objections might have some weight if
drawings made by different observers of the Solar Corona, for example,
or the Nebula of Orion, or the Milky Way had any close resemblance.
As a matter of fact, these various drawings depart far more widely
from the originals, as shown by photographic reproduction, than do
the various drawings of Mars. Mr. Fison, in his "Recent Advances in
Astronomy," in speaking of the divergence in the drawings made by
different observers, says: "In inspecting sketches of the delicate
details of the Corona of the Sun made at the same place by different
observers, it is difficult to believe that the same object has been
represented." To appreciate how widely divergent such drawings are one
has only to refer to the United States Naval Observatory publication on
the Total Eclipse of the Sun, July 29, 1878.
[Illustration: PLATE II
DRAWINGS OF THE SOLAR CORONA BY VARIOUS OBSERVERS]