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Two distinguished amateurs, meanwhile, were preparing to reassert on behalf of reflecting instruments their claim to the place of honour in the van of astronomical discovery. Of Mr. Lassell's specula something has already been said. The capabilities of the Newtonian plan were developed still more fully it might almost be said to the uttermost by the enterprise of an Irish nobleman.
Lassell's plan was a totally different one; he employed the crossed axes of the true equatoreal, and his success removed, to a great extent, the fatal objection of inconvenience in use, until then unanswerably urged against reflectors.
Sir John Herschel, in mentioning Mr. Lassell's work, did me the honour of saying "that in Mr Nasmyth he was fortunate to find a mechanist capable of executing in the highest perfection all his conceptions, and prepared by his own love of astronomy and practical acquaintance with astronomical observations, and with the construction of specula, to give them their full effect."
It accordingly forms part of the large sum of Fraunhofer's merits to have secured this inestimable advantage to observers. Sir John Herschel considered that Lassell's application of equatoreal mounting to a nine-inch Newtonian in 1840 made an epoch in the history of "that eminently British instrument, the reflecting telescope."
Among the most important of the "negative results" secured by Lassell's observations at Malta during the years 1852-53 and 1861-65, were the convincing evidence afforded by them that, without great increase of optical power, no further Neptunian or Uranian satellites can be perceived, and the consequent relegation of Herschel's baffling quartette, notwithstanding the unquestioned place long assigned to them in astronomical text-books, to the Nirvana of non-existence.
In all probability they were then for the first time seen; for although Professor Holden made out a plausible case in favour of the fitful visibility to Herschel of each of them in turn, Lassell's argument that the glare of the planet in Herschel's great specula must have rendered almost impossible the perception of objects so minute and so close to its disc, appears tolerably decisive to the contrary.
School was over till September, and now that the bugbear of final examinations was disposed of, no one seemed possessed of sufficient energy to attempt anything more strenuous than wielding a palm-leaf fan. On Amy Lassell's front porch a quartet of wilted girls lounged about in attitudes expressive of indolent ease.
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