ASTRONOMY — HALE. 75 



is a collectiou of light sources, including spark and arc in liquids or 

 in gases at any desired pressure, electric furnace, Michelson tubes 

 and mercury arc, Du Bois magnet for the Zeeman effect, etc., so 

 arranged on a circular pier that by setting a mirror at the proper 

 angle the light from any source may be focused on the slit of (i) a 

 Fuess quartz spectrograph, giving nearly the whole spectrum on 

 a single plate ; (2) a Littrow grating spectrograph of 18 feet focal 

 length ; (3) a Perot-Fabry interferometer, by Jobin, with auxiliary 

 spectroscope ; (4) a Michelson echelon spectroscope, by Hilger. It 

 is hoped that this apparatus will be of great service in the interpreta- 

 tion of solar and stellar spectra. The laboratory also contains rooms 

 for chemical experiments, photographic enlargement by electric and 

 sky light, and developing rooms. It is heated by steam, lighted by 

 electricity, and has ample electrical connections with the power-house 

 and storage batterj-. 



Warehouse. — A wooden building, 18 by 36 feet in size, has been 

 erected near the power-house for storing building materials, etc. At 

 present it is also used as a mess-house for the workmen. 



Telephone Line. — A private telephone line, extending from the 

 summit of Mount Wilson to the foot of the new trail, was constructed 

 in the early spring of 1905. It connects with the lines of the Home 

 Telephone Company, which were brought out to the foot of the trail 

 for this purpose. All of the observatory buildings, including the 

 pump-house at Strain's Camp, are in telephonic communication with 

 one another, but instruments of the telephone company, connected 

 with Pasadena, are installed only in the " Monastery " and the Snow 

 telescope-house. The service is so good that letters can be dictated 

 without difficult}- to the stenographer at the Pasadena office. 



Library. — A good working library is being purchased and installed 

 in the ' ' Monastery. ' ' It already includes complete sets of the Astro- 

 nomische Nachrichten, Zeitschrift fiir Instrumentenkunde, Bulletin 

 Astronomique, The Observatory, and Astrophysical Journal, and 

 partial sets, extending back far enough to include the literature most 

 needed in our work, of the Philosophical Magazine and the Annalen 

 der Physik. Various standard treatises have been received, and the 

 private library of the director, including sets of the Comptes Rendus, 

 Proceedings of the Royal Society, Monthly Notices of the Royal 

 Astronomical Society, Nature, and other journals, and a large col- 

 lection of papers on astrophysical subjects, is also available. We are 

 indebted to many individuals and to the directors of various observ- 

 atories for the gift of books, pamphlets, and sets of publications. 



