The reader will easily understand the joy which the safe return of the three engineers occasioned in the camp, and the intense interest with which their story of the marvels visible beyond the cloud was listened to. Their report was hastily committed to writing, sent down by the tramways, and circulated through the world with all speed. Operations were instantly resumed at the gallery, which had still to be driven through the cloud stratum. It was resolved to continue it right up to the top of the mountain, for the report of the engineers rendered it quite plain that an extensive observatory must be established there, and that a corps of the ablest mathematicians and best trained physical observers must take up their permanent abode in it, in order to investigate the nature and meaning of the myriad smaller lights and the great fiery disk. Meanwhile, daring the progress of the works, many of the artificers who were in the prime of life, repeated the ascent which had been so successfully accomplished by the three pioneers; with the guidance of the clue, this was now a comparatively easy undertaking. Before the lapse of three years the first Hesperian observatory had been actually built, and a body of twenty-five of the ablest scientific men entered upon the study of practical and theoretical astronomy in that elevated abode. As a protection against the violence of the unscreened solar rays, a cavern was excavated in which the observers could pass the daytime at their calculations, and, issuing forth at nightfall, they laboriously watched the stars. The speed with which these men found out the clue to the explanation of the complicated phenomena before them, would be quite incredible to anyone who did not bear in mind the remarkable conditions under which they worked. This was no case of a gang of stolid country bumpkins contemplating for the first time the starry heavens. Every one of the observers was an expert geometer, was perfectly familiar with all kinds of algebraical calculation, and had been trained for centuries in every type of physical observation and experiment. Before the discovery of the heavenly world telescopes had been invented; but, being adapted for use on the surface of the planet only, they were all of small size. The vast field for observation now disclosed, created a demand for a much more powerful class of instruments, and the stimulus thus given to opticians soon showed its effect in most important improvements in the manufacture of glass. Before many years were over, high class astronomical instruments were attainable, including those by which angles can be measured to an extraordinary degree of minuteness.