The opponents of the nebular hypothesis were overjoyed; they now sang paeans to astronomy, because, as they said, it had proved the truth of Scripture.

They had jumped to the conclusion that all nebula must be alike; that, if SOME are made up of systems of stars, ALL must be so made up; that none can be masses of attenuated gaseous matter, because some are not.
Science halted for a time.

The accepted doctrine became this: that the only reason why all the nebula are not resolved into distinct stars is that our telescopes are not sufficiently powerful.

But in time came the discovery of the spectroscope and spectrum analysis, and thence Fraunhofer's discovery that the spectrum of an ignited gaseous body is non-continuous, with interrupting lines; and Draper's discovery that the spectrum of an ignited solid is continuous, with no interrupting lines.
And now the spectroscope was turned upon the nebula, and many of them were found to be gaseous.

Here, then, was ground for the inference that in these nebulous masses at different stages of condensation--some apparently mere pitches of mist, some with luminous centres--we have the process of development actually going on, and observations like those of Lord Rosse and Arrest gave yet further confirmation to this view.