218 CARNEGIE INSTITUTION OF WASHINGTON. 



known. The mean systematic difference between the radial velocities, 

 as measured with the bright and dark lines, is about —20 km.; and the 

 average motion given by the bright lines, if truly representative, is the 

 greatest of any class of stars and does not differ materially from that of 

 the planetary nebulae. This coincidence, and the close resemblance of 

 the spectra of planetaries with that of R Aquarii near minimum, are 

 suggestions that will not be overlooked in future work (p. 249). 



Turning now to the Pasadena laboratory, mention should be made of 

 several important additions to its equipment. These include a 500- 

 k. w. direct-current generator set, which greatly increases the range of 

 our investigations with the arc, electric furnace, and other light-sources 

 calling for heavy current; a special solenoid magnet for the Zeeman 

 effect, designed to carry a current of 4,000 amperes, now nearly ready 

 for trial; a new electric furnace for the study of emission and absorption 

 spectra at high temperatures; a 2-inch concave grating mounted for use 

 as an auxiliary dispersion piece for work with the Fabry-Perot inter- 

 ferometer; and a large condenser and other apparatus for the produc- 

 tion of explosive discharges through fine wires. 



Mr. King's electric furnace investigations have been extended to in- 

 clude the rich spectra of several of the rare-earth metals and the infra- 

 red region of iron and manganese. The cyanogen band at X3883 has 

 also been photographed in absorption for measurement in connection 

 with Mr. St. John's work on the Einstein effect in the sun. As the 

 question has been raised whether the sensitive high-temperature lines 

 of the furnace require electrical conditions rather than high tempera- 

 ture alone, for their production, the new 500-k. w. generator has been 

 employed in testing this point. Several different means were adopted 

 to maintain the high temperature and at the same time to reduce or 

 completely eliminate the potential difference, and all were alike in 

 indicating that the low potential differences involved are without effect 

 on the spectrum (p. 258). 



With the object of imitating the spectroscopic phenomena which 

 must accompany the fall of a meteorite into the sun, Mr. Anderson has 

 exploded fine ^vires by the discharge of a large condenser. The re- 

 sulting Ught-source, attaining a brightness more than one hundred 

 times greater than that of the sun and a black-body temperature of 

 some 20,000° C, is of great interest spectroscopically. The absence 

 of the principal enhanced lines, and the reversal of the spectrum far 

 into the red, indicate the desirability of pushing this investigation fur- 

 ther (p. 262). 



The same condenser has been used by Messrs. Anderson and Babcock 

 to produce brilliant and very violent sparks for spectroscopic study. 

 The extreme characteristics of the spark spectra of iron, titanium, 

 chromium, and nickel have thus been determined for the region X3000- 

 X7200 (p. 262). 



