The Mysterious Island (17 page)

Then, after some minutes thought—

"Herbert," he asked of the lad, "is not this the 15th of April?"

"Yes, captain," replied Herbert.

"Well, if I am not mistaken, to-morrow will be one of the four days in
the year in which the real time is identical with average time; that
is to say, my boy, that to-morrow, to within some seconds, the sun will
pass the meridian just at midday by the clocks. If the weather is fine
I think that I shall obtain the longitude of the island with an
approximation of some degrees."

"Without instruments, without sextant?" asked Gideon Spilett.

"Yes," replied the engineer. "Also, since the night is clear, I will
try, this very evening, to obtain our latitude by calculating the
height of the Southern Cross, that is, from the southern pole above the
horizon. You understand, my friends, that before undertaking the work
of installation in earnest it is not enough to have found out that this
land is an island; we must, as nearly as possible, know at what distance
it is situated, either from the American continent or Australia, or from
the principal archipelagoes of the Pacific."

"In fact," said the reporter, "instead of building a house it would
be more important to build a boat, if by chance we are not more than a
hundred miles from an inhabited coast."

"That is why," returned Harding, "I am going to try this evening to
calculate the latitude of Lincoln Island, and to-morrow, at midday, I
will try to calculate the longitude."

If the engineer had possessed a sextant, an apparatus with which the
angular distance of objects can be measured with great precision, there
would have been no difficulty in the operation. This evening by the
height of the pole, the next day by the passing of the sun at the
meridian, he would obtain the position of the island. But as they had
not one he would have to supply the deficiency.

Harding then entered the Chimneys. By the light of the fire he cut two
little flat rulers, which he joined together at one end so as to form
a pair of compasses, whose legs could separate or come together. The
fastening was fixed with a strong acacia thorn which was found in the
wood pile. This instrument finished, the engineer returned to the beach,
but as it was necessary to take the height of the pole from above a
clear horizon, that is, a sea horizon, and as Claw Cape hid the southern
horizon, he was obliged to look for a more suitable station. The best
would evidently have been the shore exposed directly to the south; but
the Mercy would have to be crossed, and that was a difficulty. Harding
resolved, in consequence, to make his observation from Prospect Heights,
taking into consideration its height above the level of the sea—a
height which he intended to calculate next day by a simple process of
elementary geometry.

The settlers, therefore, went to the plateau, ascending the left bank of
the Mercy, and placed themselves on the edge which looked northwest and
southeast, that is, above the curiously-shaped rocks which bordered the
river.

This part of the plateau commanded the heights of the left bank, which
sloped away to the extremity of Claw Cape, and to the southern side of
the island. No obstacle intercepted their gaze, which swept the horizon
in a semi-circle from the cape to Reptile End. To the south the horizon,
lighted by the first rays of the moon, was very clearly defined against
the sky.

At this moment the Southern Cross presented itself to the observer in an
inverted position, the star Alpha marking its base, which is nearer to
the southern pole.

This constellation is not situated as near to the antarctic pole as the
Polar Star is to the arctic pole. The star Alpha is about twenty-seven
degrees from it, but Cyrus Harding knew this and made allowance for
it in his calculation. He took care also to observe the moment when it
passed the meridian below the pole, which would simplify the operation.

Cyrus Harding pointed one leg of the compasses to the horizon, the
other to Alpha, and the space between the two legs gave him the angular
distance which separated Alpha from the horizon. In order to fix the
angle obtained, he fastened with thorns the two pieces of wood on a
third placed transversely, so that their separation should be properly
maintained.

That done, there was only the angle to calculate by bringing back the
observation to the level of the sea, taking into consideration the
depression of the horizon, which would necessitate measuring the height
of the cliff. The value of this angle would give the height of Alpha,
and consequently that of the pole above the horizon, that is to say, the
latitude of the island, since the latitude of a point of the globe is
always equal to the height of the pole above the horizon of this point.

The calculations were left for the next day, and at ten o'clock every
one was sleeping soundly.

The next day, the 16th of April, and Easter Sunday, the settlers issued
from the Chimneys at daybreak, and proceeded to wash their linen. The
engineer intended to manufacture soap as soon as he could procure the
necessary materials—soda or potash, fat or oil. The important question
of renewing their wardrobe would be treated of in the proper time and
place. At any rate their clothes would last at least six months longer,
for they were strong, and could resist the wear of manual labor. But
all would depend on the situation of the island with regard to inhabited
land. This would be settled to-day if the weather permitted.

The sun rising above a clear horizon, announced a magnificent day, one
of those beautiful autumn days which are like the last farewells of the
warm season.

It was now necessary to complete the observations of the evening before
by measuring the height of the cliff above the level of the sea.

"Shall you not need an instrument similar to the one which you used
yesterday?" said Herbert to the engineer.

"No, my boy," replied the latter, "we are going to proceed differently,
but in as precise a way."

Herbert, wishing to learn everything he could, followed the engineer to
the beach. Pencroft, Neb, and the reporter remained behind and occupied
themselves in different ways.

Cyrus Harding had provided himself with a straight stick, twelve feet
long, which he had measured as exactly as possible by comparing it with
his own height, which he knew to a hair. Herbert carried a plumb-line
which Harding had given him, that is to say, a simple stone fastened
to the end of a flexible fiber. Having reached a spot about twenty feet
from the edge of the beach, and nearly five hundred feet from the cliff,
which rose perpendicularly, Harding thrust the pole two feet into
the sand, and wedging it up carefully, he managed, by means of the
plumb-line, to erect it perpendicularly with the plane of the horizon.

That done, he retired the necessary distance, when, lying on the sand,
his eye glanced at the same time at the top of the pole and the crest of
the cliff. He carefully marked the place with a little stick.

Then addressing Herbert—"Do you know the first principles of geometry?"
he asked.

"Slightly, captain," replied Herbert, who did not wish to put himself
forward.

"You remember what are the properties of two similar triangles?"

"Yes," replied Herbert; "their homologous sides are proportional."

"Well, my boy, I have just constructed two similar right-angled
triangles; the first, the smallest, has for its sides the perpendicular
pole, the distance which separates the little stick from the foot of the
pole and my visual ray for hypothenuse; the second has for its sides
the perpendicular cliff, the height of which we wish to measure, the
distance which separates the little stick from the bottom of the
cliff, and my visual ray also forms its hypothenuse, which proves to be
prolongation of that of the first triangle."

"Ah, captain, I understand!" cried Herbert. "As the distance from the
stick to the pole is to the distance from the stick to the base of the
cliff, so is the height of the pole to the height of the cliff."

"Just so, Herbert," replied the engineer; "and when we have measured the
two first distances, knowing the height of the pole, we shall only have
a sum in proportion to do, which will give us the height of the cliff,
and will save us the trouble of measuring it directly."

The two horizontal distances were found out by means of the pole, whose
length above the sand was exactly ten feet.

The first distance was fifteen feet between the stick and the place
where the pole was thrust into the sand.

The second distance between the stick and the bottom of the cliff was
five hundred feet.

These measurements finished, Cyrus Harding and the lad returned to the
Chimneys.

The engineer then took a flat stone which he had brought back from one
of his previous excursions, a sort of slate, on which it was easy
to trace figures with a sharp shell. He then proved the following
proportions:—

15:500::10:x

500 x 10 = 5000

5000 / 15 = 333.3

From which it was proved that the granite cliff measured 333 feet in
height.

Cyrus Harding then took the instrument which he had made the evening
before, the space between its two legs giving the angular distance
between the star Alpha and the horizon. He measured, very exactly, the
opening of this angle on a circumference which he divided into 360 equal
parts. Now, this angle by adding to it the twenty-seven degrees which
separated Alpha from the antarctic pole, and by reducing to the level of
the sea the height of the cliff on which the observation had been made,
was found to be fifty-three degrees. These fifty-three degrees being
subtracted from ninety degrees—the distance from the pole to the
equator—there remained thirty-seven degrees. Cyrus Harding concluded,
therefore, that Lincoln Island was situated on the thirty-seventh degree
of the southern latitude, or taking into consideration through the
imperfection of the performance, an error of five degrees, that it must
be situated between the thirty-fifth and the fortieth parallel.

There was only the longitude to be obtained, and the position of the
island would be determined, The engineer hoped to attempt this the same
day, at twelve o'clock, at which moment the sun would pass the meridian.

It was decided that Sunday should be spent in a walk, or rather an
exploring expedition, to that side of the island between the north of
the lake and Shark Gulf, and if there was time they would push their
discoveries to the northern side of Cape South Mandible. They would
breakfast on the downs, and not return till evening.

At half-past eight the little band was following the edge of the
channel. On the other side, on Safety Islet, numerous birds were gravely
strutting. They were divers, easily recognized by their cry, which much
resembles the braying of a donkey. Pencroft only considered them in
an eatable point of view, and learnt with some satisfaction that their
flesh, though blackish, is not bad food.

Great amphibious creatures could also be seen crawling on the sand;
seals, doubtless, who appeared to have chosen the islet for a place of
refuge. It was impossible to think of those animals in an alimentary
point of view, for their oily flesh is detestable; however, Cyrus
Harding observed them attentively, and without making known his idea, he
announced to his companions that very soon they would pay a visit to the
islet. The beach was strewn with innumerable shells, some of which would
have rejoiced the heart of a conchologist; there were, among others, the
phasianella, the terebratual, etc. But what would be of more use, was
the discovery, by Neb, at low tide, of a large oysterbed among the
rocks, nearly five miles from the Chimneys.

"Neb will not have lost his day," cried Pencroft, looking at the
spacious oyster-bed.

"It is really a fortunate discovery," said the reporter, "and as it is
said that each oyster produces yearly from fifty to sixty thousand eggs,
we shall have an inexhaustible supply there."

"Only I believe that the oyster is not very nourishing," said Herbert.

"No," replied Harding. "The oyster contains very little nitrogen, and
if a man lived exclusively on them, he would have to eat not less than
fifteen to sixteen dozen a day."

"Capital!" replied Pencroft. "We might swallow dozens and dozens without
exhausting the bed. Shall we take some for breakfast?"

And without waiting for a reply to this proposal, knowing that it would
be approved of, the sailor and Neb detached a quantity of the molluscs.
They put them in a sort of net of hibiscus fiber, which Neb had
manufactured, and which already contained food; they then continued to
climb the coast between the downs and the sea.

From time to time Harding consulted his watch, so as to be prepared in
time for the solar observation, which had to be made exactly at midday.

All that part of the island was very barren as far as the point
which closed Union Bay, and which had received the name of Cape South
Mandible. Nothing could be seen there but sand and shells, mingled with
debris of lava. A few sea-birds frequented this desolate coast, gulls,
great albatrosses, as well as wild duck, for which Pencroft had a great
fancy. He tried to knock some over with an arrow, but without result,
for they seldom perched, and he could not hit them on the wing.

This led the sailor to repeat to the engineer,—

"You see, captain, so long as we have not one or two fowling-pieces, we
shall never get anything!"

"Doubtless, Pencroft," replied the reporter, "but it depends on you.
Procure us some iron for the barrels, steel for the hammers, saltpeter.
coal and sulphur for powder, mercury and nitric acid for the fulminate,
and lead for the shot, and the captain will make us first-rate guns."