TRANSACTIONS OF SECTION A. 623 



Objective and the 28 and 15-incli specula formerly used by Dr. Draper. These 

 specula have not yet been mounted, but preparations for doing so are in active 

 progress. The objective above mentioned, and also an 8-inch photographic tele- 

 scope, have for some time been employed in the work, -which has been described in 

 the published report on the Henry Draper Memorial. The photographs sent 

 herewith and described below illustrate the progress of this work. 



1. View of the buildings of the observatory, taken from a point to the north- 

 west of them. The building at the right of the view contains the 11-inch 

 Draper telescope, and the small building in the foreground at the extreme left 

 contains the 8-inch photographic telescope. 



2. Interior of the building first mentioned, showing the 11-inch telescope. 



3. View of the building containing the 8-inch telescope, showing the construc- 

 tion of the roof. 



4. View of the present state of the building now in process of construction for 

 the 28-inch reflector above mentioned. 



5. Spectra of a Cygni and a Tauri taken with the 11-inch objective and 

 enlarged in the maimer described in the Draper ^lemorial Ileport. 



G. Spectra of o C'efi (showing bright lines) and of a Canis Minoris. 



7. Spectra of a Canis Majoris, a Cygni, a Canis Minoris, a Aia-ir/ce, and 

 a Bootis, brought together upon one print for convenience of comparison. In the 

 orio-inal negative the H line in a Cygni is shown distinctly double; but this effect 

 is unfortunately lost in the process of enlargement and silver printing. 



8. A copy of the Draper Memorial Ileport above mentioned, explaining the 

 process employed in obtaining the spectra shown in Nos. 5, 6, and 7, and contain- 

 ino- a plate which shows the progress made in these researches since their 

 commencement. 



9. Glass positive, showing the spectrum of ^ Ononis obtained through a layer 

 of hyponitric fumes, for the purpose of determining the wave-lengths of lines in 

 the stellar spectra as proposed on page 9 of the report. The principal lines of the 

 stellar spectrum are marked with ink on the glass side of the plate. Nearly all 

 the other lines shown are due to the fumes. 



10. Glass positive of a Lyra showing the H line double. 



11. Glass positive of f Ursce Majoris, showing the K line double. A faint 

 spectrum of the star near f is also shown on the same plate. 



12. Glass positive showing the extreme blue end of the spectrum of a Canis 

 Majoris. The shorter spectrum shown on tlie same plate represents the same star 

 photographed with a shorter exposure, and therefore exhibiting the detail of the 

 Ijrighter portion of the spectrum, which is lost by over-exposure in the spectrum 

 showing the extreme blue end. 



The spectra shown in the views numbered 5 and 6 are enlarged about five times ; 

 those in No. 7 about three times. The cylindrical lens was used in these enlarge- 

 ments, as described in the Report. 



The glass positives Nos. 9, 10, 11, and 12 are made directly from the original 

 negatives, and give a very good idea of the spectrum as originally obtained by the 

 11-inch telescope. These positives, and also the paper print No. 7, represent 

 recent work, which is now made public for the first time. 



A wide field for study is now open in the comparison of the different spectra 

 thus obtained, and in their consequent classification. The behaviour of the metals 

 under variations of temperature and pressure far beyond those which we can con- 

 trol in the laboratory are here exhibited. In the course of these researches 

 various cosmic problems will suggest themselves, especially when we employ the 

 greater light-collecting power of the 28-inch reflector and apply this to the pecu- 

 liar spectra of some of the fainter stars. The special work for this instrument will 

 be the study of variable stars, with a view to obtaining some knowledge of the 

 cause of their variation. The 11-inch telescope will be largely employed in the 

 study of the movements of stars in the line of sight. 



