Before long Lord Rosse, after regrinding the great mirror, obtained better views of the mysterious nebula. Even now, however, he could use but half the power of the telescope, yet at length the doubts of astronomers as to the resolvability of the nebula were removed. 'We could plainly see,' he wrote to Professor Nichol, 'that all about the trapezium was a mass of stars, the rest of the nebula also abounding with stars, and exhibiting the characteristics of resolvability strongly marked.' These views were abundantly confirmed by subsequent observations with the great mirror.

It will surprise many to learn that even Lord Rosse's great reflector is surpassed in certain respects by some of the exquisite refractors now constructed by opticians. As a light-gatherer the mirror is, of course, unapproachable by refractors. Even if it were possible to construct an achromatic lens six feet in diameter, yet, to prevent flexure, a thickness would have to be given to the glass which would render it almost impervious to light and therefore utterly useless. But refractors have a power of definition not possessed by large reflectors. With a refractor eight inches only in aperture, for instance, Mr. Dawes has obtained better views of the planets (and specially of Mars), than Lord Rosse's six-feet speculum would give under the most favourable circumstances. And in like manner, the performance of Lord Rosse's telescope on the Orion nebula has been surpassedso far as resolution into discrete stars is concerned-by the exquisite defining power of the noble refractor of Harvard College (U.S.). By means of this instrument hundreds of stars have been counted within the confines of the once intractable nebula.

It seemed, therefore, that all doubt had vanished from the subject which had so long perplexed astronomers. 'That was proved to be real,' Nichol wrote, 'which, with conceptions of space enlarged even as Herschel's, we deemed incomprehensible.'

Yet even at this stage of the inquiry there were found minds bold enough to question whether a perfectly satisfactory solution of the great problem had really been attained. Nor is it difficult, I think, to point out strong reasons for such doubts. I shall content myself by naming one which has always appeared to me irresistible.

The Orion nebula as seen in powerful telescopes covers a large extent of the celestial sphere. According to the Padre Secchi, who observed it with the great Merz refractor of the observatory at Rome, the nebulous region covers a triangular space, the width of whose base is some eight times, while its height is more than ten times as great as the moon's apparent diameter,a space more than fifty times greater than that covered by the moon. Now, I do not say that it is inconceivable that an outlying star-system, so far off as to be irresolvable by any but the most powerful telescopes, should cover so large a space on the heavens. On the contrary, I do not believe that a galaxy resembling our own would be resolvable at all, unless it were so near as to appear much larger than the Orion nebula. I believe astronomers have been wholly mistaken in considering any of the nebulas to be such systems as our own. There may be millions of such systems in space, but I am very certain no telescope we could make would suffice to resolve any of them. But what I do consider inconceivable, is, that a nebula extending so widely, and placed (as supposed) beyond our system, should yet appear to cling (as the Orion nebula undoubtedly does) around the fixed stars seen in the same field with it. So strongly marked is this characteristic, that Sir John Herschel (who failed, apparently, to see its meaning) mentions amongst others no less than four stars, - one of which is the bright middle star of the belt-as ' involved in strong nebulosity,' while the intermediate nebulosity is only just traceable. The probability that this arrangement is accidental is so small as to be almost evanescent.

However, as I have said, English astronomers, almost without a dissentient voice, accepted the resolution of the nebula as a proof that it represents a distant star-system resembling our own galactic system, but far surpassing it in magnitude.

The time came, however, when a new instrument, more telling even than the telescope, was to be directed upon the Orion nebula, and with very startling results.

The spectroscope had revealed much respecting the constitution of the fixed stars. We had learned that they are suns resembling our own. It remained only to show that the Orion nebula consists of similar suns, in order to establish beyond all possibility of doubt the theories which had been so complacently accepted. A very different result rewarded the attempt, however. When Dr. Huggins turned his spectroscope towards the great nebula, he saw, in place of a spectrum resembling the sun's, three bright lines only! A spectrum of this sort indicates that the source of light is a luminous gas, so that whatever the Orion nebula may be, it is most certainly not a congeries of suns resembling our own.

It would be unwise to theorise at present on a result so remarkable. Nor can we assert that Herschel's speculations have been confirmed, though his general reasoning has been abundantly justified. Astronomers have yet to do much before they can interpret the mysterious entity which adorns Orion's sword. On every side, however, observations are being made which give promise of the solution of this and kindred difficulties. We have seen the light of comets analysed by the same powerful instrument; and we learn that the light from the tail and coma is similar in quality (so far as observation has yet extended) to that emitted from the Orion nebula. We see, therefore, that in our own solar system we have analogues of what has been revealed in external space. I would not, indeed, go so far as to assert that the Orion nebula is a nest of cometic systems; but I may safely allege that there is now not a particle of evidence that the nebula lies beyond our galaxy.

Nor need we doubt the accuracy of Lord Rosse's observations. More than a year before his death, indeed, he mentioned to Dr. Huggins 'that the matter of the great nebula in Orion had not been resolved by his telescope. In some parts of the nebula he observed a large number of exceedingly minute red stars. These red stars, however, though apparently connected with the irresolvable blue material of the nebula, yet seemed to be distinct from it.'

The whole subject seems to be as perplexing as any that has ever been submitted to astronomers. Time, however, will doubtless unravel the thread of the mystery. We may safely leave the inquiry in the hands of the able observers and physicists whose attention has been for a long time directed towards it. And we need only note, in conclusion, that in the southern hemisphere there exists an object equally mysterious-the great nebula round n Argus - which has yielded similar results when tested with the spectroscope. The examination of this mysterious nebula, associated with the most remarkable variable in the heavens - a star which at one time shines but as a fifth magnitude star, and at another exceeds even the brilliant Canopus in splendour-may, for aught that is known, throw a new light on the constitution of the great Orion nebula.

From Fraser's Magazine for February 1869.