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Updated: August 6, 2024
While, just as we inferred that, according to circumstances, the extent to which aggregation has been carried must vary; so we find that, in fact, there are regular nebulæ of all degrees of resolvability, from those consisting of innumerable minute masses, to those in which their numbers are smaller and the sizes greater, and to those in which there are a few large bodies worthy to be called stars.
"The Nubecula Major, like the Minor, consists partly of large tracts and ill-defined patches of irresolvable nebula, and of nebulosity in every stage of resolution, up to perfectly resolved stars like the Milky Way, as also of regular and irregular nebulæ properly so called, of globular clusters in every stage of resolvability, and of clustering groups sufficiently insulated and condensed to come under the designation of 'clusters of stars." Cape Observations, p. 146.
On the subject of their nature his views underwent a remarkable change. Finding that his potent instruments resolved into stars many nebulous patches in which no signs of such a structure had previously been discernible, he naturally concluded that "resolvability" was merely a question of distance and telescopic power. The singular variety of their appearance was thus described by him:
How I longed to discover the secret of some perfect lens, whose magnifying power should be limited only by the resolvability of the object, and which at the same time should be free from spherical and chromatic aberrations in short, from all the obstacles over which the poor microscopist finds himself continually stumbling!
The brightness of objects situated in its nearer portions, therefore, cannot be much exaggerated, nor that of its remoter much enfeebled, by their difference of distance; yet within this globular space, we have collected upwards of six hundred stars of the seventh, eighth, ninth, and tenth magnitudes, nearly three hundred nebulæ, and globular and other clusters, of all degrees of resolvability, and smaller scattered stars innumerable of every inferior magnitude, from the tenth to such as by their multitude and minuteness constitute irresolvable nebulosity, extending over tracts of many square degrees.
It cannot be contended that, on the average, the apparent sizes of the stars indicate their distances, without its being admitted that, on the average, the apparent sizes of the nebulæ indicate their distances that, generally speaking, the larger are the nearer and the smaller are the more distant. Mark, now, the necessary inference respecting their resolvability.
How I longed to discover the secret of some perfect lens, whose magnifying power should be limited only by the resolvability of the object, and which at the same time should be free from spherical and chromatic aberrations, in short from all the obstacles over which the poor microscopist finds himself continually stumbling!
On looking at the Sun, I was at once struck with the apparent resolvability of its mottled appearance. The whole disc of the Sun, so far as I examined it, appeared to be covered over with relatively bright rice-like particles, and the mottled appearance seemed to be produced by the interlacing of these particles.
How I longed to discover the secret of some perfect lens whose magnifying power should be limited only by the resolvability of the object, and which at the same time should be free from spherical and chromatic aberrations, in short from all the obstacles over which the poor microscopist finds himself continually stumbling!
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