gone into numerous smaller stars. Accepting this view, it would follow that the material in question was a sheet so thin that the thickness of the space filled by the cluster was an appreciable fraction of that occupied

Fig. 1. Photograph showing Structure of the Milky Way, by Barnard.

by the stars. In other words, one-fifth of the stars of the region would be contained in a thin sheet. This result seems too improbable to be accepted.

The other and more likely conclusion is that the number of very