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."Well, if I am not mistaken, to-morrow will be one of the four days in the year in which the real time isidentical with average time; that is to say, my boy, that to-morrow, to within some seconds, the sun will passthe meridian just at midday by the clocks.If the weather is fine I think that I shall obtain the longitude of theisland 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 latitudeby calculating the height of the Southern Cross, that is, from the southern pole above the horizon.Youunderstand, my friends, that before undertaking the work of installation in earnest it is not enough to havefound out that this land is an island; we must, as nearly as possible, know at what distance it is situated, eitherfrom 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 bychance 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 bemeasured with great precision, there would have been no difficulty in the operation.This evening by theheight of the pole, the next day by the passing of the sun at the meridian, he would obtain the position of theisland.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 joinedtogether at one end so as to form a pair of compasses, whose legs could separate or come together.Thefastening 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 clearhorizon, that is, a sea horizon, and as Claw Cape hid the southern horizon, he was obliged to look for a moresuitable station.The best would evidently have been the shore exposed directly to the south; but the Mercywould have to be crossed, and that was a difficulty.Harding resolved, in consequence, to make hisobservation from Prospect Heights, taking into consideration its height above the level of the sea--a heightwhich 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 onthe edge which looked northwest and southeast, that is, above the curiously-shaped rocks which bordered theriver.This part of the plateau commanded the heights of the left bank, which sloped away to the extremity of ClawCape, and to the southern side of the island.No obstacle intercepted their gaze, which swept the horizon in asemi-circle from the cape to Reptile End.To the south the horizon, lighted by the first rays of the moon, wasvery clearly defined against the sky.At this moment the Southern Cross presented itself to the observer in an inverted position, the star Alphamarking its base, which is nearer to the southern pole.The Mysterious Island 67 The Mysterious IslandThis constellation is not situated as near to the antarctic pole as the Polar Star is to the arctic pole.The starAlpha is about twenty-seven degrees from it, but Cyrus Harding knew this and made allowance for it in hiscalculation.He took care also to observe the moment when it passed the meridian below the pole, whichwould simplify the operation.Cyrus Harding pointed one leg of the compasses to the horizon, the other to Alpha, and the space between thetwo legs gave him the angular distance which separated Alpha from the horizon.In order to fix the angleobtained, he fastened with thorns the two pieces of wood on a third placed transversely, so that theirseparation 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 thecliff.The value of this angle would give the height of Alpha, and consequently that of the pole above thehorizon, that is to say, the latitude of the island, since the latitude of a point of the globe is always equal to theheight 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.Chapter 14The next day, the 16th of April, and Easter Sunday, the settlers issued from the Chimneys at daybreak, andproceeded to wash their linen.The engineer intended to manufacture soap as soon as he could procure thenecessary materials--soda or potash, fat or oil.The important question of renewing their wardrobe would betreated of in the proper time and place.At any rate their clothes would last at least six months longer, for theywere strong, and could resist the wear of manual labor.But all would depend on the situation of the islandwith 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 whichare 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 cliffabove 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 [ Pobierz całość w formacie PDF ]