Suddenly a brilliant idea struck me. Immediately opposite the point on the islet at which I wished to land, there was a broad strip of sandy beach, constituting indeed part of the margin of the basin, of which the islet formed the centre. Would it be possible to make my measurements from that point? There could be no harm in trying, at all events, and we accordingly pulled across the water, landing at a part of the beach that looked eminently promising. The first thing was to determine the direction of a line running due south from the topmost pinnacle of the obelisk rock, and after a few trials with the compass, I got this. My next act was to erect a line perpendicular to this along the sandy margin of the basin, which I accomplished with the aid of my sextant, taking care to make this second line as long as the nature of the ground would allow. Then, driving a peg into the sand at the intersection of these two lines, and another at the farther extremity of my second line, I had a right-angled triangle, whereof the two pegs and the obelisk rock marked the angles. I had now only to measure very carefully my second line, which I did by means of a surveyor's tape measure, bought at Sydney for the purpose, and to take the angle between the perpendicular and the hypothenuse of my triangle, when I had the means of calculating all or any of the elements of the triangle that I desired. In this way, then, I ascertained that the pinnacle of the obelisk rock was exactly six thousand four hundred and seventy-seven feet due north of the peg I had driven into the sand to mark the intersection of my two lines. Then, returning to this same peg, I sent Forbes away to the islet in the boat, with instructions to set up one of the oars, with a white pocket-handkerchief attached to it, on the shore of the islet at the precise spot I should indicate to him by signal. This spot I arranged to be exactly in line with the peg and the obelisk rock; all three points, therefore, were in one straight line, the bearing of which was due north and south, while its northern extremity was the obelisk rock. My next task was to take an angle to the oar from the peg at which I had taken the angle to the obelisk rock, which enabled me to determine that the oar was three thousand eight hundred and two feet from the intersecting peg, and consequently two thousand six hundred and seventy-five feet from the obelisk rock. This completed all the data I required; for I had now only to drive a bold, conspicuous staff into the sand in place of my intersecting peg, and another into the ground on the islet where the oar now stood, and by cutting back into the scrub for a distance of one thousand six hundred and seventy-five feet toward the obelisk rock, using these two staves as guides to keep their line straight, the workers would reach a spot exactly a thousand feet south from the obelisk rock; or, in other words, the hiding-place of the treasure.