From the Earth to the Moon/Chapter XXIV
On the 20th of October in the preceding year, after the close of the subscription, the president of the Gun Club had credited the Observatory of Cambridge with the necessary sums for the construction of a gigantic optical instrument. This instrument was designed for the purpose of rendering visible on the surface of the moon any object exceeding nine feet in diameter.
At the period when the Gun Club essayed their great experiment, such instruments had reached a high degree of perfection, and produced some magnificent results. Two telescopes in particular, at this time, were possessed of remarkable power and of gigantic dimensions. The first, constructed by Herschel, was thirty-six feet in length, and had an object-glass of four feet six inches; it possessed a magnifying power of 6,000. The second was raised in Ireland, in Parsonstown Park, and belongs to Lord Rosse. The length of this tube is forty-eight feet, and the diameter of its object-glass six feet; it magnifies 6,400 times, and required an immense erection of brick work and masonry for the purpose of working it, its weight being twelve and a half tons.
Still, despite these colossal dimensions, the actual enlargements scarcely exceeded 6,000 times in round numbers; consequently, the moon was brought within no nearer an apparent distance than thirty-nine miles; and objects of less than sixty feet in diameter, unless they were of very considerable length, were still imperceptible.
In the present case, dealing with a projectile nine feet in diameter and fifteen feet long, it became necessary to bring the moon within an apparent distance of five miles at most; and for that purpose to establish a magnifying power of 48,000 times.
Such was the question proposed to the Observatory of Cambridge, There was no lack of funds; the difficulty was purely one of construction.
After considerable discussion as to the best form and principle of the proposed instrument the work was finally commenced. According to the calculations of the Observatory of Cambridge, the tube of the new reflector would require to be 280 feet in length, and the object-glass sixteen feet in diameter. Colossal as these dimensions may appear, they were diminutive in comparison with the 10,000 foot telescope proposed by the astronomer Hooke only a few years ago!
Regarding the choice of locality, that matter was promptly determined. The object was to select some lofty mountain, and there are not many of these in the United States. In fact there are but two chains of moderate elevation, between which runs the magnificent Mississippi, the "king of rivers" as these Republican Yankees delight to call it.
Eastwards rise the Appalachians, the very highest point of which, in New Hampshire, does not exceed the very moderate altitude of 5,600 feet.
On the west, however, rise the Rocky Mountains, that immense range which, commencing at the Straights of Magellan, follows the western coast of Southern America under the name of the Andes or the Cordilleras, until it crosses the Isthmus of Panama, and runs up the whole of North America to the very borders of the Polar Sea. The highest elevation of this range still does not exceed 10,700 feet. With this elevation, nevertheless, the Gun Club were compelled to be content, inasmuch as they had determined that both telescope and Columbiad should be erected within the limits of the Union. All the necessary apparatus was consequently sent on to the summit of Long's Peak, in the territory of Missouri.
Neither pen nor language can describe the difficulties of all kinds which the American engineers had to surmount, of the prodigies of daring and skill which they accomplished. They had to raise enormous stones, massive pieces of wrought iron, heavy corner-clamps and huge portions of cylinder, with an object-glass weighing nearly 30,000 pounds, above the line of perpetual snow for more than 10,000 feet in height, after crossing desert prairies, impenetrable forests, fearful rapids, far from all centers of population, and in the midst of savage regions, in which every detail of life becomes an almost insoluble problem. And yet, notwithstanding these innumerable obstacles, American genius triumphed. In less than a year after the commencement of the works, toward the close of September, the gigantic reflector rose into the air to a height of 280 feet. It was raised by means of an enormous iron crane; an ingenious mechanism allowed it to be easily worked toward all the points of the heavens, and to follow the stars from the one horizon to the other during their journey through the heavens.
It had cost $400,000. The first time it was directed toward the moon the observers evinced both curiosity and anxiety. What were they about to discover in the field of this telescope which magnified objects 48,000 times? Would they perceive peoples, herds of lunar animals, towns, lakes, seas? No! there was nothing which science had not already discovered! and on all the points of its disc the volcanic nature of the moon became determinable with the utmost precision.
But the telescope of the Rocky Mountains, before doing its duty to the Gun Club, rendered immense services to astronomy. Thanks to its penetrative power, the depths of the heavens were sounded to the utmost extent; the apparent diameter of a great number of stars was accurately measured; and Mr. Clark, of the Cambridge staff, resolved the Crab nebula in Taurus, which the reflector of Lord Rosse had never been able to decompose.