On a new group of lines in the photographic spectrum of Sirius

In 1879, I gave an account of a series of broad lines in the photographic region of the spectrum which was found to be characteristic of Sirius, Vega., and other white stars, and which was identified as a continuation of the spectrum of hydrogen beyond H. In the photographs of Sirius which I had taken up to that time, I was not able to be certain if the two most refrangible of the lines,θ andl , were present. This uncertainty has been set at rest by photographs taken since, in which the complete series of the hydrogen lines, includingθ andl , come out with great distinctness.