Make an astrolabe, and obtain the latitude of the island, and, by an
eclipse of the moon, the longitude also. By means of the Epitome make
a chart on Mercator's projection, and find out the distance from any
known land.
I found in my book a description of an instrument used by the ancients
to ascertain altitudes and to measure angles, called an Astrolabe,
which, upon careful study and examination of the cut, I felt confident
would serve my purpose admirably. So to work I went, and in this
manner. I made first a strong four-legged stool or bench, about three
feet in height and four feet long, and two feet wide upon the top. I
then took some nice planed pieces of my dark hardwood and made a smooth
surface about an inch thick and five feet square. On this, afterwards
to be erected on the stool at right angles like an inverted letter T,
I drew a circle with a pair of immense dividers that I made for this
purpose, taking in all the area possible, which made my circle about
fifty-nine inches in diameter, leaving a margin of one inch,--supposing
my inches to have been of the right length; and this I determined by
the length of the knuckle of my thumb, which I formerly used for quick
measurement, and from which standard I constructed the only rule
I ever have used on the island. How nearly correct it is I have no
means of knowing. This groove I impressed into the wood by repeatedly
turning the dividers around the circumference. I then went to work
and subdivided this circle into degrees and minutes, which I did by
marking the circle once across at any angle passing through the centre
mark, and then by another mark crossing this one at exactly right
angles, which I determined by means of my dividers--as laid down in
Bowditch's Epitome--by the use of them at equal distances from the
centre on the line already marked, sweeping them till the two lines
crossed beyond the circumference, making a small mark there so as to
erect a perpendicular on the base already drawn. This cut my circle
at once into quadrants of 90° each, and these were subdivided again
in like manner. I made the circle large on purpose, so as to be able
to mark it plainly to sections of one minute each, and by its size
to avoid any error in any angle, the chances of which were greatly
decreased by every inch of diameter. As I constructed it, I had nearly
one-half an inch of circumference to mark sixty minutes upon, and as
I only subdivided one of the quadrants it did not take me very long,
each degree being represented by a space slightly smaller than a half
inch, which was a good large scale to work upon. Having finished the
marking of my board I nailed it firmly to the stool in an upright
position, with the quadrant, that I had carefully subdivided on the
marked circumference, pointing with one of its angles to zenith, and
the other on a line with the top of the stool. I then procured a nice
straight piece of cane some six feet in length and about an inch in
diameter, and with a heated rod of iron burned out all the pith between
each joint till I had made a nice tube of that length. Just within the
aperture at one end I fastened with a little fish glue a large strong
hair from the beard of one of my goats. I then fastened, by means of
a hole through the centre of my upright disc, this tube or telescope
to it on the side that was subdivided into degrees, and about an inch
from the face. I fastened this so that it was held firmly in place,
and yet could be moved upon its centre by the pressure of my hand on
either arm. This tube I then furnished with a small delicate pin on
the outside, in an exact line with the stretched hair inside the tube,
and pointing to the degrees and minutes on the marked circumference
on the disc, which it almost touched. In other words, if I moved one
arm of the tube, the needle on the outside would follow the grooved
circumference on the disc, and upon being released would mark some
given degree or minute. Having gotten this machine all in order and
complete, I placed it one day so as to examine the sun near noon, and
here is how I obtained my latitude. What I was doing now was not so
very difficult. I well knew that there were several ways to determine
latitude. I was aware that the difference of a minute or two even in
my altitude, as apparently observed, would not disturb my computation
more than a mile or so. In fact each minute marked upon the disc
practically stood for one mile of latitude, and the mean of several
observations would correct even any errors from this cause.
I waited till I knew that it was nearly noon by the appearance of the
sun, and then commenced operations. In the first place I aimed my tube
at the sun, and to be able to do so without injuring my eye, I would
say that I had fitted the orifice of the tube nearest to me with a
piece of smoke-colored membrane or backbone of the squid, which is as
transparent as glass, and very thin and delicate. Having, by moving
the tube with my hand, brought the sun so that it seemed to stand upon
the hair in the outer end of the tube, or like a great capital O upon
a base line [O_], I left it carefully in that position for a moment or
two, and then applied my eye again, and found, as I supposed, that the
sun no longer seemingly rested upon the hair in my tube, but had risen,
which forced me to again lower the arm nearest me and elevate the
other extremity, and proved to me that it was not yet noon, and that
the sun had not yet reached the meridian. This I did many times, till
at last the sun seemed for a minute or so to stand still, as sailors
say, and I knew that it was at meridian. I took good care not to touch
the instrument, but waited quietly till, by glancing through it, I saw
in a few moments the disc of the sun, or lower limb as it is termed,
begin to drop below the hair in my tube, and I was then positive that
it had passed the meridian. Being assured of this, I went carefully to
the marked circumference on the upright disc and noted carefully the
degree and minute to which the needle in the side of the tube pointed,
which in this case was 54° 51'. Having carefully marked this down with
ink upon birch bark, I went again to the other end of the tube, and,
elevating it, brought the outer end down toward the sea till the hair
and the horizon seemed to be one. I then again carefully observed the
degree and minute at which the needle pointed, which in this case was
7° 16', and my task was done; for, by subtracting 7° 16' from 54° 51'
I obtained 47° 35', which was exactly the apparent altitude of the sun
at noon on September 22, 1866, civil account; and, having that, it was
easy to determine the latitude in the following manner:--
At noon observe the altitude of the sun's lower limb
bearing North 47° 35'
Add for semi-diameter, dip, etc. 12'
----------
47° 47'
Subtract from 90° 00'
----------
Sun's zenith distance 42° 13' S.
Declination for longitude, say 115° W 8' S.
----------
Latitude by observation 42° 21' S.
Thus I demonstrated the latitude of my island; but now for the
longitude. To obtain that I knew that I must first ascertain the time
at the island: I could do nothing without that; for longitude was,
as I well knew, simply time changed into degrees. I thought of fifty
different ways to obtain correct time, but believed none of them
sufficiently accurate for my purpose. I could make a sundial for one
thing, find out the length of the day by the Epitome and Nautical
Almanac, make candles to burn such a length of time, sand to run down
an inclined plane at such a rate, but none of these would do.
The difference of a minute, or one-sixtieth of a degree, in an observed
altitude would only affect, as I have said, my latitude just one
mile, whilst an error of time of one minute from true time would, as
I was well aware, throw my longitude out just fifteen miles; hence it
behoved me to have exact time if I desired to get exact longitude, and
therefore I saw nothing for it but that I must construct a clock, and
at it I went. It was not such an enormous undertaking after all. Of
course I should make it of wood, and in my boyhood I knew many wooden
clocks that kept excellent time; besides, if I could only construct
something that would keep time for an hour or two without much error,
it would answer my purpose. If I had a clock that I could set at noon
by my observation, nearly correct, I could correct it perfectly by an
afternoon observation, and have for an hour or so true time, even if it
did gain or lose a few minutes in twenty-four hours. So to work I set,
and soon turned out the few small wheels necessary, and the weight and
pendulum for the same. I spent little time upon the non-essentials, but
put it together inside my house on the wall, open so that I could get
at it, and furnished it with wooden hands and a thin wooden face.
After I had arranged it and found that it would tick, and by
observations at noon for a few days been able to regulate the pendulum,
I went diving into the Epitome and the Nautical Almanac as to how
I should utilize it so as to get my longitude, after all; when one
evening, in turning over the Nautical Almanac, which was calculated for
1866, 1867, 1868, and 1869, my eye fell upon the following, and I felt
that my task was done:--
Total eclipse of the moon, September 30,1866, invisible at Greenwich,
visible in South America, South Pacific Ocean, and parts of Africa,
Asia, and Indian Ocean.
FORMULA (CIVIL ACCOUNT).
Day. Hour. Min.
Moon enters penumbra 30 5 44 A.M.
Moon enters shadow 30 6 53 "
Total phase begins 30 8 49 "
Total phase ends 30 9 39 "
Moon leaves shadow 30 10 45 "
Moon leaves penumbra 30 11 55 "
This was all I needed to verify my longitude past peradventure, and I
went to work at once, calculating when the eclipse ought to take place,
nearly, with me.
At a rough calculation I knew that my island was situated somewhere
between the 110° and 120° of longitude west of Greenwich, that is to
say, in the neighborhood of seven hours' difference of time later than
Greenwich time. Therefore I knew that if the moon entered the penumbra
at Greenwich (although invisible) on the 30d. 5h. 44 min. A.M. that
I ought to look for it to occur visibly to my eyes somewhere from one
to two o'clock in the afternoon of the same day, or seven hours later.
The _exact_ difference in the time between Greenwich and that to be
observed on my island, changed into degrees and minutes, would, of
course be the true longitude west of Greenwich.
It was with the utmost anxiety that I awaited the coming of the 30th
of September, for it all depended upon pleasant weather whether or not
I should be able to make my observation. I placed my astrolabe so as
to be able to move it quickly in any needed direction, as I intended
to use the tube to look at the sun through so as not to blind my eyes.
I also prepared my birch bark in the house, and commenced practising
myself in counting seconds, for I should have to leave my instrument
and go to the house, counting all the time to note the time marked
by my clock. I found upon practice that I could not make this work
very successfully, and that according to the state of my feelings or
excitement I counted long and short minutes. This would not do; I must
invent something better; and I finally bethought myself of counting the
beatings of my pulse with the finger of one hand upon the wrist of the
other, and applying the proportion to the interval between the observed
time by my clock.
The morning at last came that I so much desired, and nothing could be
more beautiful than the balmy, spring-like day that surrounded me. The
sky was cloudless and the sun shone down in splendor through a clear
and pure atmosphere. The morning passed slowly away, and it seemed
as if the moon and sun would never approach each other; but finally,
in the afternoon, the heavens showed me that the eclipse would soon
take place, and I made my arrangements to take four observations, as
follows: Time when moon entered shadow; time when total phase began;
time when total phase ended; time when moon left shadow.
Nothing could have been better than the afternoon I experienced to make
these observations, and in less than six hours the whole affair was
over, with the following result, I having carefully regulated my clock
as near as possible by an observation at noon:--
Day. Hour. Min.
Moon enters shadow at island (civil account) 30 2 50 P.M.
Moon enters shadow at Greenwich 30 6 53 A.M.
------------------------
Difference 7 57
Total phase begins at island 30 4 48 P.M.
Total phase begins at Greenwich 30 8 49 A.M.
------------------------
Difference 7 59
Total phase ends at island 30 5 34 P.M.
Total phase ends at Greenwich 30 9 39 A.M.
------------------------
Difference 7 55
Moon leaves shadow at island 30 6 41 P.M.
Moon leaves shadow at Greenwich 30 10 45 A.M.
------------------------
Difference 7 56
Hours. Min.
Sum of differences, four observations 31 47
Hours. Min. Sec.
Mean of same 7 56 45
Which, reduced to time, gives the longitude of the island 119° 11'
15'' west of Greenwich.
There, my problem was done and I was for the moment happy. Perhaps
some will wonder why I cared to obtain the latitude and longitude
of my island at all. Let me explain. My Bowditch's Epitome gave the
latitude and longitude of all prominent capes, harbors, headlands,
light-houses, etc., in the whole Pacific Ocean. In other words, knowing
now the latitude and longitude of my own island, I had only to project
a chart on Mercator's projection, pricking off the relative positions
of the land on all sides of me, as well as the position of my island,
to have a practical and useful chart. Of course I should not be able
to draw the coast line or the circumference of any island, but my
chart would show just what latitude and longitude Easter Island was
in, for instance, and just how far and in exactly what direction my
island lay from it. Also, how far I was from the American coast, and
the exact distance and course from any of the principal ports such as
Lima, Valparaiso, Pisco, etc. How far from New Zealand and the Society
Islands, and in what direction from them.
Having marked the exact latitude and longitude of each of these places,
which were fully given in the Epitome, on my chart, I could call upon
my memory often to fill in the coast lines, and even if I should in
the case of the islands, make them even imaginary, there would be no
harm done, for the little black star on each would show me where the
latitude and longitude met exactly, and I should be furnished with a
practical chart as far as sea navigation was concerned, but not one
that would be of much account in entering any harbors.
I cannot say that at this time I had any fixed plan of escaping from
the island, but I very well knew that nothing in the world would aid
me so much in the attempt as to know the position in latitude and
longitude that the island occupied, and a chart of the surrounding
seas, with its numerous islands and headlands on the main land. It can
well be conceived that my first task after determining the position of
my island was to turn to the Epitome to ascertain the nearest land to
me there marked down, and after diligent search this is what I found:--
"Easter Island Peak," 27° 8' south latitude and 109° 17' west longitude.
"Island," 28° 6' south latitude and 95° 12' west longitude.
"Group of Islands," 31° 3' south latitude and 129° 24' west longitude.
"Massafuera," 33° 45' south latitude and 80° 47' west longitude, which
I speedily worked out, by the principles of Mercator's sailing, to be
in course and distance from my island, as follows:--
Course. Distance.
Easter Island Peak N. N. E. 1/2 E. 1,040 miles.
Island N. E. 3/4 E. 1,440 "
Group of Islands N. W. 3/4 N. 840 "
Massafuera N. N. E. 1/4 E. 1,540 "
Of these four places only two ever had a name, and I did not know
whether Easter Island was inhabited or not, and about Massafuera I was
totally ignorant.
Easter Island, I knew, of course, was one of the so-called Society
Islands, and was the nearest practical land to which I could escape.
But how was I safely to pass over a thousand miles of water? This
investigation only proved to me what I had so long feared, namely, that
my island was out of the track of all trade, and that it would be a
miracle should I be preserved by the arrival of any vessel. I knew now
that I must really give up all hope in that direction, and set to work
seriously to help myself.
I therefore applied myself with great vigor to my chart which I
outlined upon nice goatskin parchment, which I glued together till I
had a surface nearly four feet square, upon which I could lay out all
the Pacific Ocean on a nice, large scale, by Mercator's projection.
I went on with my daily work, and made this matter one for evening
amusement, and as I pricked off the latitude and longitude of some
well-known place, that I in former years had visited, my heart swelled
within me with grief and mortification, and I had often to stop and
wipe the tears from my eyes before I could proceed.
Release from my prison seemed farther from me than ever, as I advanced
in my task, and although I had a sort of morbid pleasure in my work,
and a fascination to linger over it, yet I saw plainly that I was
indeed cast away; for what could I do alone in a boat, even supposing
that I could build one strong enough to resist one thousand miles of
water? Who was to steer when I was asleep? and then supposing I should
be able to arrive at Easter Island, what guarantee had I that I should
not be murdered at once by the natives?
No, here I was fixed beyond fate upon my own island, where, with the
exception of companionship, I had everything that human heart could
wish for. But on the other hand, without companionship I lacked
everything that is worth living for in this world. I felt that the
problem of all problems hereafter to me would be how can I escape to
some civilized country in safety? And from what I now knew, it seemed
as if it would remain a problem till my bones were left whitening in
the Hermitage.
My discovery of the latitude and longitude of the island had brought me
no comfort, and I felt much more uneasy now than I did before finishing
my task. But as the summer weather came on, I regained to a degree
my good spirits, keeping, however, the problem of escape continually
working in my mind, for I knew that there must be some way to solve it,
especially with the resources that I had gathered around about me.