Local System and Draper Extension 71
it undoubtedly indicates the presence of an obscuring dark
cosmic cloud, and it is in the discovery and location in space
of such obscurations that the Henry Draper Extension may
be most useful.
Figure 9. Class K stars of magnitudes 10.1 to 11.0 in the Taurus
region of the Henry Draper Extension.
To look further into the form and effect of the obscura-
tion at Sh 20m, ⅛25o, and also in the field fifteen degrees
further south, I have presented in Figures 11 and 12 a
series of distribution plots of Class A stars. All the Class A