286 CARNEGIE INSTITUTION OF WASHINGTON. 



sists of a base-plate through which the current conductors and tubes 

 for the water-cooling system are passed, and an iron hood which is 

 lowered into position when all parts of the apparatus have been fully 

 adjusted. With this furnace, tube temperatures above 3,000° can 

 be maintained for long periods, and many phenomena, especially of 

 absorption spectra, can be studied more effectively than heretofore. 



The two high-tension transformers, producing voltages up to 60,000 

 and 100,000, respectively, have been completely overhauled. The 

 100,000-volt transformer has been provided with a new tank for oil 

 insulation. 



Messrs. Nicholson and Pettit have devoted some time to the design 

 and construction of thermopiles and vacuum cells for use in labora- 

 tory, solar, planetary, and stellar problems. Special attention was 

 paid to tellurium, which has given excellent results in vacuo when used 

 in combination with silver and other metals. A preliminary study of 

 the change of sensitivity with pressure gives similar effects in hydrogen, 

 oxygen, and air, indicating that the entire change takes place between 

 1 mm. and 0.01 mm. pressure. Further studies will be made at lower 

 pressures. Tests of the couples for the observation of the total energy 

 curve across the sun's disk with improvised photometric apparatus 

 have given satisfactory records. 



ELECTRIC-FURNACE INVESTIGATIONS. 



The following studies of electric furnace spectra were carried out 

 during the year by Mr. King. 



Manganese. 



The material previously collected was supplemented by some addi- 

 tional spectrograms and prepared for publication. In the interval 

 X2795 to X6605, 270 manganese lines were classified according to their 

 changes, with temperatures varying from 1560° to 2400° C. The 

 search for manganese furnace-lines was extended as far as X8200. 

 Besides the usual classification, the special features exhibited by note- 

 worthy lines at different temperatures were described. 



Scandium. 



The acquisition of a small quantity of the rare element scandium 

 in the oxide form made possible the study of the furnace spectrum of 

 this element, which was highly desirable on account of the prominence 

 of scandium in the sun. Furnace spectrograms were made at 2000°, 

 2250°, and 2600° C. for the interval X3000 to X6600; 307 lines were 

 classified according to intensity at the three furnace temperatures 

 and in the arc. Special interest attaches to the enhanced lines and to 

 those strengthened at low temperatures. In the sun, only the en- 

 hanced Imes of scandium are well marked in the disk spectrum, the 

 arc lines in general being very faint. Though usually absent from the 

 solar disk, the low-temperature lines are strong in the spot spectrum. 



