thereby effecting a saving of light, which fully compensated for any loss caused by the mirror being placed askew. The concave mirror made by Herschel alone weighed a ton, to say nothing of the enormous tube and its fittings. Herschel had consequently to invent a special apparatus for holding and moving this gigantic instrument. The moving gear consisted of a mass of beams, pulleys and cords, reminding one more of the rigging of a ship than of a philosophical instrument. The apparatus for moving the telescope appeared so complicated to the casual observer, although in reality it was very simple, that it doubtless contributed in no small degree to the propagation of the fanciful stories we have already spoken of.
The performances of this splendid instrument hardly came up to the expectations of those who saw it in progress. Herschel, it is true, was enabled by its means to use a power of from 3 to 6,000, but he could only use these amplifications on a few objects—the planets, for instance, giving so little light under a high power as to become indistinct and misty. In 1802 Baron von Zach, in his Monthly Astronomical Compendium, went so far as to say that this colossal instrument was not of the slightest utility, that no discovery had ever been made with it, and that it ought to be considered merely as an optical curiosity. Subsequent events, however, proved very conclusively that Baron von Zach was utterly wrong in his statements and prophecies.
The telescope constructed by Herschel, although very wonderful for the day in which it was made, has long since been eclipsed by that belonging to Lord Rosse, and erected by his late father at Birr Castle, near Parsonstown in Ireland. It is superior to Herschel's instrument both in point of size, and workmanship. The late Lord Rosse, not fearing that his dignity would be compromised by such an act, went boldly to
