Untitledtwo groups are thoroughly well mixed; it is not a case of an innerstream going one way and an outer stream the other. But there are notquite as many stars going one way as the other. For every two stars inone stream there are three in the other. Now, as we have said, someeminent astronomers hold that the spiral nebulæ are universes like ourown, and if we look at the two photographs (Figs. 25 and 26) we see thatthese spirals present features which, in the light of what we have justsaid about our system, are very remarkable. The nebula in Coma Berenicesis a spiral edge-on to us, and we see that it has precisely thelens-shaped middle and the general flattened shape that we have found inour own system. The nebula in Canes Venatici is a spiral facing towardsus, and its shape irresistibly suggests motions along the spiral arms.This motion, whether it is towards or away from the central, lens-shapedportion, would cause a double streaming motion in that central portionof the kind we have found in our own system. Again, and altogether apart
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