plates, and the photographic brightness of the star.

2. _Catalogue of Spectra of Faint Stars_.--This work resembles the
preceding, but is much more extensive. The same instrument is used, but
each region has an exposure of an hour, the rate of the clock being such
that the width of the spectrum will be as before 0.1 cm. Many stars of
the ninth magnitude will thus be included, and nearly all brighter than
the eighth. In one case, over three hundred spectra are shown on a
single plate. This work has been carried on only in the intervals when
the telescope was not needed for other purposes. 99 plates have,
however, been obtained, and on these 4,442 spectra have been measured.
It is proposed to complete the equatorial zones first, gradually
extending the work northward. In all, 15,729 spectra of bright and faint
stars have been measured.

3. _Detailed Study of the Spectra of the Brighter Stars_.--This work has
been carried on with the 11 inch photographic telescope used by Dr.
Draper in his later researches. A wooden observatory was constructed
about 20 feet square. This was surmounted by a dome having a clear
diameter of 18 feet on the inside. The dome had a wooden frame, sheathed
and covered with canvas. It rested on eight cast iron wheels, and was
easily moved by hand, the power being directly applied. Work was begun
upon it in June, and the first observations were made with the telescope
in October.

Two prisms were formed by splitting a thick plate of glass diagonally.
These gave such good results that two others were made in the same way,
and the entire battery of four prisms is ordinarily used. The safety and
convenience of handling the prisms is greatly increased by placing them
in square brass boxes, each of which slides into place like a drawer.