During these preparations Harding arranged everything for his astronomical observation.  He chose a clear place on the shore, which the ebbing tide had left perfectly level.  This bed of fine sand was as smooth as ice, not a grain out of place.  It was of little importance whether it was horizontal or not, and it did not matter much whether the stick six feet high, which was planted there, rose perpendicularly.  On the contrary, the engineer inclined it towards the south, that is to say, in the direction of the coast opposite to the sun, for it must not be forgotten that the settlers in Lincoln Island, as the island was situated in the Southern Hemisphere, saw the radiant planet describe its diurnal arc above the northern, and not above the southern horizon.

Herbert now understood how the engineer was going to proceed to ascertain the culmination of the sun, that is to say its passing the meridian of the island or, in other words, determine due south.  It was by means of the shadow cast on the sand by the stick, a way which, for want of an instrument, would give him a suitable approach to the result which he wished to obtain.

In fact, the moment when this shadow would reach its minimum of length would be exactly twelve o’clock, and it would be enough to watch the extremity of the shadow, so as to ascertain the instant when, alter having successively diminished, it began to lengthen.  By inclining his stick to the side opposite to the sun, Cyrus Harding made the shadow longer, and consequently its modifications would be more easily ascertained.  In fact, the longer the needle of a dial is, the more easily can the movement of its point be followed.  The shadow of the stick was nothing but the needle of a dial.  The moment had come, and Cyrus Harding knelt on the sand, and with little wooden pegs, which he stuck into the sand, he began to mark the successive diminutions of the stick’s shadow.  His companions, bending over him, watched the operation with extreme interest.  The reporter held his chronometer in his hand, ready to tell the hour which it marked when the shadow would be at its shortest.  Moreover, as Cyrus Harding was working on the 16th of April, the day on which the true and the average time are identical, the hour given by Gideon Spilett would be the true hour then at Washington, which would simplify the calculation.  Meanwhile as the sun slowly advanced, the shadow slowly diminished, and when it appeared to Cyrus Harding that it was beginning to increase, he asked, “What o’clock is it?”

“One minute past five,” replied Gideon Spilett directly.  They had now only to calculate the operation.  Nothing could be easier.  It could be seen that there existed, in round numbers, a difference of five hours between the meridian of Washington and that of Lincoln Island, that is to say, it was midday in Lincoln Island when it was already five o’clock in the evening in Washington.  Now the sun, in its apparent movement round the earth, traverses one degree in four minutes, or fifteen degrees an hour.  Fifteen degrees multiplied by five hours give seventy-five degrees.