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, after having successively diminished, it began to lengthen.