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THE EVOLUTION OF WORLDS
that it is not made up of stars, certainly big enough for us to see. On the other hand, from the fact that its spectrum is continuous it must be solid or liquid. Young pointed out that this did not follow, because a gas under great pressure also gives a continuous
Nebula N. G. C. 1499 Persei—after Roberts.
spectrum. But he forgot that here no such pressure could exist. A nebula of compressed gas could not have an irregular form and would have, in the case of the Andromeda nebula, a mass so enormous as to preclude supposition. Continuity of spectrum here means discontinuity of mass. The spectral solidity of the nebula speaks of a status quo ante, not of a condition of condensation now going on.
