In the original negatives of subjects 10 and 12, there are faint darkrings immediately surrounding some of the stars in the denser parts of thenebulosity. This effect has no doubt been accentuated in the subsequentphotographic processes. On the plates of these two subjects in thecompleted volume, these rings are very distinct and give rise to asuspicion that the effect has been enhanced by the engraver. A criticalexamination of the prints seems to confirm this view. In the originalproofs these rings were inconspicuous and were not noticed. The processesof steel-facing and printing appear to have increased the effect markedly,as it is much stronger on the sheets printed for the edition than in anyof the early proofs.

Inasmuch as these effects were not and could not be discovered until thesheets were assembled in Sacramento for binding, it has not been thoughtdesirable to delay the issue of the volume for several weeks additional inorder to have new plates and new prints of these subjects made by thedistant engraver.

Lick Observatory,
Mount Hamilton,
November, 1908.