Quite the contrary, it formed part of the cliffs and black mountains themselves.  Some stupendous volcanic upheaval of the remote past had cleft the mountain wall, and had extruded through the “fault” a huge “dyke” of virgin metal—­to use technical terms.  This golden dyke, two and a half to three miles wide and of undeterminable length and depth, had merely been formed by strong, cunning hands into walls, battlements, houses, mosques, and minarets.

It had been carved out in situ, the soft metal being fashioned with elaborate skill and long patience.  Jannati Shahr seemed, on a larger scale and a vastly more magnificent plan, something like the hidden rock-city of Petra in the mountains of Edom—­a city wholly carved by the Edomites out of the solid granite, without a single stone having been laid in mortar.

Wonderful beyond all words as the early afternoon sun gleamed from its broad-flung golden terraces and mighty walls—­whereon uncounted thousands of white figures had massed themselves—­the “Very Heavenly City” widened to the Legionaries’ gaze.

On, up the last slope of the grassy plain the rushing horsemen bore.  Into a broad, paved way they thundered, and so up, on, toward the great gate of virgin gold now waiting to receive them.

CHAPTER XL

INTO THE TREASURE-CITADEL

Well might those Legionaries who had been left behind to protect Nissr and the sacred gifts have envied the more fortunate ones now sweeping into Jannati Shahr.  The rear guard, however, formed no less essential a part of the undertaking than the main body of the Legion.

This rear guard consisted of Grison, Menendez, Prisrend, Frazier, and Manderson.  Their orders were as follows:  If the main body did not return by midnight, or if sounds of firing were heard from the city, or again if they received direct orders via the Master’s pocket wireless, they were at once to load the machine-guns on board the liner.  They were to carry Myzab on board, also, and with the wireless spark detonate the explosive which would reduce the Black Stone to dust.

This accomplished, they were to start the engines and, if possible, make a getaway—­which might be feasible for five men.  If they succeeded, they were to wheel over the city and drop the second kappa-bomb, also all the remaining explosive, by way of punitive measures.  Well-placed hits might wipe out most of the city and, with it, the population which had broken the Oath of the Salt.

The main body of the Legion would, of course, also perish in this debacle if still alive; but the probability existed that before Nissr could take the air, all would be dead.

The program was explicit.  All five men of the rear guard fully understood its every detail and all had sworn to carry it out to the letter.  Their morale remained perfect; their discipline, under the command of Grison—­left alone as they were in the midst of potentially hostile territory and with overwhelming masses of Mohammedans close at hand—­held them as firmly as did that of the advance guard now whirling up the wide, paved road to the gleaming gate of Jannati Shahr.