The spectra of all stars of the sixth magnitude and brighter will generally be found upon these plates, except in the case of red stars.  Many fainter blue stars also appear.  Three or four exposures are made upon a single plate.  The entire sky north of -24 deg. would be covered twice, according to this plan, with 180 plates and 690 exposures.  It is found preferable in some cases to make only two exposures; and when the plate appears to be a poor one, the work is repeated.  The number of plates is therefore increased.  Last summer the plates appeared to be giving poor results.  Dust on the prisms seemed to be the explanation of this difficulty.  Many regions were reobserved on this account.  The first cycle, covering the entire sky from zero to twenty-four hours of right ascension, has been completed.

The work will be finished during the coming year by a second cycle of observations, which has already been begun.  The first cycle contains 257 plates, all of which have been measured, and a large part of the reduction completed. 8,313 spectra have been measured on them, nearly all of which have been identified, and the places of a greater portion of the stars brought forward to the year 1900, and entered in catalogue form.  In the second cycle, 64 plates have been taken, and about as many more will be required. 51 plates have been measured and identified, including 2,974 spectra.  A study of the photographic brightness and distribution of the light in the spectra will also be made.

The results will be published in the form of a catalogue resembling the Photometric Catalogue given in volume xiv. of the Annals of Harvard College Observatory.  It will contain the approximate place of each star for 1900, its designation, the character of the spectrum as derived from each of the plates in which it was photographed, the references to these 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.