Interstellar cloud of dust, hydrogen, helium and other ionized gases.
1One of the few nebulæ known to vary in brightness and form.
2On many of the diagrams the position of nebulæ is indicated.
3It is a constellation rich in double and multiple stars, clusters, and nebulæ.
4Many of the nebulæ serve as tests both for illumination and defining power.
5Ether, atoms, and nebulæ are the raw material of their trade.
6We could not refuse to admit as possible such an origin for nebulæ.
7Indeed, it is a question whether all nebulæ are not to some extent spiral.
8She and --are twin nebulæ who think themselves constellations.
9They are full of nebulæ and star-clusters, and show striking evidences of spiral movement.
10Since then it has been shown to be a prominent constituent of nebulæ and hot stars.
11Laplace's famous theory was that the planets and the earth were formed from great whirling nebulæ.
12We now come to a still more extraordinary phenomenon of this kind -the Pleiades nebulæ.
13Yet no speculation upon the origin of species or the function of the nebulæ filled his mind.
14Hundreds of thousands of nebulæ, besides even vaster irregular stretches of nebulous matter, exist in the heavens.
15No stars, no nebulæ, no meteoric matter, nor even the smallest particle of cosmic dust-absolutelyempty space.
16The wonderful aspect of the admixtures of nebulæ and star-clusters in Sagittarius has been described in Chapter 1.