The object in question was at no time, subsequently to 1805, visible to the naked eye. Its aspect in Sir John Herschel's great reflector on the 23rd of September, 1832, was described by him as that of a "conspicuous nebula," nearly 3 minutes in diameter. No trace of a tail was discernible. While he was engaged in watching it, a small knot of minute stars was directly traversed by it, "and when on the cluster," he tells us,[254] it "presented the appearance of a nebula resolvable and partly resolved into stars, the stars of the cluster being visible through the comet." Yet the depth of cometary matter through which such faint stellar rays penetrated undimmed, was, near the central parts of the globe, not less than 50,000 miles. It is curious to find that this seemingly harmless, and we may perhaps add effete body, gave occasion to the first (and not the last) cometary "scare" of an enlightened century. Its orbit, at the descending node, may be said to have intersected that of the earth; since, according as it _bulged in or out_ under the disturbing influence of the planets, the passage of the comet was affected _inside_ or _outside_ the terrestrial track. Now, certain calculations published by Olbers in 1828[255] showed that, on October 29, 1832, a considerable portion of its nebulous surroundings would actually sweep over the spot which, a month later, would be occupied by our planet. It needed no more to set the popular imagination in a ferment. Astronomers, after all, could not, by an alarmed public, be held to be infallible. Their computations, it was averred, which a trifling oversight would suffice to vitiate, exhibited clearly enough the danger, but afforded no guarantee of safety from a collision, with all the terrific consequences frigidly enumerated by Laplace. Nor did the panic subside until Arago formally demonstrated that the earth and the comet could by no possibility approach within less than fifty millions of miles.[256]