of the sky which
it adorns. Sir John Herschel describes it as one of the most
extraordinary objects in the heavens.

The 'Crab' Nebula in Taurus, the 'Horse-Shoe' Nebula in Sobieski's
Shield, and the 'Dumb-Bell' Nebula in Vulpecula are remarkable objects,
but the assistance of a powerful telescope is required to bring out
their distinctive features. The 'Crab' Nebula is partially resolvable
into stars; the other two are believed to be gaseous.

The largest and most remarkable of all the nebulae is that known as the
Great Nebula in Orion, which was discovered and delineated by Huygens in
the middle of the seventeenth century. It is perceptible to the naked
eye, and when viewed with a glass of low power can be seen as a circular
luminous haze surrounding the multiple star Theta Orionis--one of the
stars in the Giant's Sword, and which is of itself a remarkable object.
The most conspicuous part of the nebula bears a slight resemblance to
the wing of a bird; it consists of flocculent masses of nebulous matter
possessing a faint greenish tinge. Sir John Herschel compared it to a
surface studded over with flocks of wool, or to the breaking up of a
mackerel sky when the clouds of which it consists begin to assume a
cirrous appearance. Its brightest portion is occupied by four
conspicuous stars, which form a trapezium; around each there is a dark
space free from nebulosity, a circumstance which would seem to indicate
that the stars possess the power either of absorbing or of repelling the
nebulous matter in their immediate vicinity. When observed with a
powerful telescope, this nebula appears to be of vast dimensions, and,
with its effluents, occupies an area of 4 deg. by 5-1/2 deg.. Irregular
branching masses, streams, sprays, filaments, and curved spiral wreaths
project outward from the parent mass, and become gradually lost in the
surrounding space. This object remained for long a profound mystery; no
telescope was capable of resolving it, nor was it known what this
'unformed fiery mist, the chaotic material of future suns,' was, until
the spectroscope revealed that it consists of a stupendous mass of
incandescent gases--nitrogen, hydrogen, and other elementary substances,
occupying a region of space believed by some to equal in extent the
whole stellar system to which our Sun belongs.

In the Southern Hemisphere, near to the pole of the equator, are two
nebulous clouds of unequal size; the larger having an area about four