NEW STAR IN THE CONSTELLATION AURIGA. 53 



maximum about the 7th or 8th. [Compare the curve in fig. 3, and the table on p. 58, 

 which have been extended so as to include the subsequent observations.] Not one of 

 the four novse of modern times has exhibited a curve of this character, at least as far as 

 one can judge from the present available data for Nova Aurigse. 



From Dr Becker I have received the most satisfactory results, derived from observa- 

 tions made on February 3, 4, and 5, and again on the 10th and 11th. [These results 

 were exhibited to the Society in a graphic form, but it is here preferable to give 

 Dr Becker's written account of the observations as received from him on February 16.] 



Observations of the Bright Lines in the Spectrum of Nova Aurigce, 

 made at Dunecht by Dr L. Becker. 



The day after the discovery of the new star was announced, I left for Dunecht 

 Observatory in order to observe its spectrum with the 15-inch refractor. The large 

 spectroscope by Cooke, with a collimator 24 inches in length, having already been 

 removed to Edinburgh, I employed in my observations the . smaller spectroscope by 

 Grubb, the same with which Professor Copeland had made the greater part of his former 

 observations. The collimator of this instrument has 7 inches focal length, and an effective 

 pencil of light 0'6 inch in diameter; the viewer is 10 inches in length, and turns by a 

 worm-screw with a divided head working against a sector which can be clamped to the 

 prism-box. The prism is kept in a fixed position. In these observations a compound 

 prism was used at the minimum deviation for b. On the first night, February 3, a power 

 of 14 diameters was used, but on the following nights one of 7. For comparison I 

 employed the sodium and lithium lines, and the lines of the zinc-lead spark spectrum, as 

 produced by a 5 -inch induction coil in connection with a Leyden-jar. The light from the 

 spark passes through a lens, and is reflected to the upper and lower part of the slit by a 

 small silver mirror, which is fixed in front of the slit and has an opening for allowing the 

 light from the object-glass to pass. The same battery which works the coil serves to 

 illuminate the field of view by reflection from the last surface of the prism, and also to 

 produce bright wire illumination. By means of a small rheostat, which is clamped to 

 the sector, the light may be moderated, while a switch enables the observer to put either 

 the incandescent lamps or the coil into circuit. This arrangement, which I introduced 

 in the last weeks of my stay at Dunecht in 1889, is very convenient if the observer has 

 to observe without assistance. In reducing the observations to wave-lengths (Potsdam 

 system) I first determined, once for all, 4 constants of Ketteler's formula of dispersion 

 from measures of four solar lines equidistant between A and H, and computed a table 

 giving the wave-length as a function of the readings of the screw. The deviations of 

 this curve from the one given by the observations of solar lines are so small that they may 

 be determined with great accuracy by the graphical method. The lines of the spark 

 spectrum were measured along with the solar lines, the latter being at the centre part of 

 the slit, the former below and above. Although the values of their wave-lengths thus 



