220 CARNEGIE INSTITUTION OF WASHINGTON. 



bright stellar images, together with the means of photographing their 

 spectra under high dispersion. Experiments made by Adams with 

 the 60-inch reflector, which was designed with this object in view, gave 

 excellent large-scale spectra of some of the brightest stars. The 

 ground was thus prepared for further work, with higher dispersion, 

 which will be done with the 100-inch telescope as soon as the powerful 

 spectrograph required for this purpose can be completed and mounted 

 in its constant-temperature chamber on the massive concrete pier 

 south of the polar axis. 



Other elements in the design of the Hooker telescope have the same 

 general object in view — that of developing and applying in astronom- 

 ical practice the effective research methods suggested by recent ad- 

 vances in physics. Although most of our major instruments are now 

 completed and in use, this policy must remain as a dominant factor in 

 our plan of research. Fresh possibilities of progress are constantly 

 arising, and these must be utilized as rapidly as circumstances permit. 

 Examples have been mentioned in the solar and stellar fields, but those 

 of the laboratory itself must not be overlooked. 



The policy of providing for the interpretation of celestial phenomena 

 by laboratory experiments was an important element in the initial 

 organization of the Mount Wilson Observatory. Although a wide 

 departure from the customary practice of most large observatories, 

 it was by no means without precedent, and it certainly has been justi- 

 fied by results. Indeed, the development of many of our chief solar 

 investigations would have been impossible without the aid of special 

 laboratory studies, going hand in hand with the astronomical observa- 

 tions. So indispensable are such researches, and so great is the promise 

 of their extension, that the time has come to advance them from a 

 minor or accessory feature of the Observatory establishment to full 

 equaUty with the major factors in its work. 



The first step toward this end has just been taken by the purchase 

 from the General Electric Company of a 500-kilowatt motor-generator 

 set, soon to be installed in our Pasadena laboratory. The heavy 

 current (D. C, 220 volts, 4,000 amperes) generated by this machine 

 will be used in the first instance to actuate an extremely powerful 

 electromagnet, designed by Anderson for the extension of our researches 

 on the Zeeman effect and for other related investigations. Within the 

 large and uniform field of this magnet, which will be built in the form of 

 a solenoid, a special electric furnace, designed for this purpose by King, 

 will be used for the study of the inverse Zeeman effect at various angles 

 with the Unes of force — a piece of work urgently needed to interpret 

 certain remarkable anomalies in the magnetic phenomena of sun-spots. 

 Furthermore, with this new and powerful equipment it will be possible 

 to study the combined effect of magnetic and electric fields on radia- 

 tion, to extend previous investigations on the spectrum of the "tube- 



