Again, the condensation of the Aether, composed as it is of its atoms, ever in a state of rotation, does away with the Primitive impulse which was objected to in Art. 9. For in that article it was shown that the conception of a primitive impulse as conceived by Newton was unphilosophical, in that its conception was not simple, and failed to satisfactorily account for observed phenomena. With the hypothesis, however, of a rotatory aetherial atom, we have at once those conditions which at any time, in the history of the universe, may give rise to those conditions by which a body may be set rotating not only on its axis, but also revolving around some central body, as the process of condensation is continued. So that in the primordial and universal electro-magnetic Aether that exists in all space, we get those conditions which will not only give rise to the phenomena of light, heat, magnetism and electricity, but also those properties, qualities and motions by which are produced, maintained and perpetuated, the various bodies that exist in the Aether, which is at once the physical source and cause of the bodies. ART. 122. _Kinds of Nebulae._--Nebulae may be classified into the following groups-- 1. Irregular Nebulae. 2. Ring and Elliptical Nebulae. 3. Spiral or Whirlpool Nebulae. 4. Planetary Nebulae. _Irregular Nebulae._--Of this class the most conspicuous are those in the constellations of Orion and Andromeda. So clearly defined are they, that they are oftentimes seen by the naked eye on a clear night, and are often mistaken for comets.