MOUNT WILSON SOLAR OBSERVATORY. 271 



formula connecting proper motion with parallax. The observations 

 of Mr. van Maanen on small proper-motion stars will soon provide the 

 material for a revision of this standard, which now appears to give values 

 of the parallax that are too small. As an illustration, spectrum observa- 

 tions on 7 of the stars measured by Mr. van Maanen give the following 

 comparison: Measured parallax, +0T013; parallax from proper mo- 

 tion, +0T006 ; parallax from spectrum, +0''004. For the large proper- 

 motion stars of measured parallax the agreement, as would be expected, 

 is distinctly better. 



The Spectrum of Nova Geminorum No. 2. 



Photographs of the spectrum of Nova Geminorum of 1912, made by 

 Mr. Pease with the small spectrograph at the principal focus of the 

 60-inch reflector, show that the spectrum of this star has now passed 

 from that resembling a planetary nebula into that of a Wolf-Rayet 

 star. Similar results were found for Nova Aurigse of 1891 and Nova 

 Persei of 1901 from photographs made in 1913-14. Special interest 

 attaches to the result in the case of Nova Geminorum No. 2, since the 

 observations form essentially a continuous series from the time of its 

 outburst as a temporary star and record the changes in its spectrum 

 through the various stages of its development into what is probably its 

 final state, that of a Wolf-Rayet star. The conclusion that at least a 

 portion of the Wolf-Rayet stars are Novse in the later stages of their 

 history is made highly probable by these results. 



A remarkable feature of the observations was the disappearance of 

 the chief nebular line at X 5007 previous to that of the second nebular 

 line at X4960. These hues have always been associated with each 

 other and vary in intensity with one another in planetary nebulae. 

 They are almost certainly due to the same radiating gas, and the differ- 

 ence in their behavior in this case argues a highly exceptional state of 

 physical conditions. 



The Spectrum of T Tauri. 



A low dispersion photograph of the spectrum of T Taiu-i shows that 

 the spectrum of this irregular variable is composite in character. The 

 spectrum of the star proper is of type approximately F5, but super- 

 posed upon it are narrow, bright hues which appear to extend beyond 

 the continuous spectrum of the star. There seems to be httle doubt 

 that the star is surrounded by an extensive atmosphere similar to that 

 of the star B.D.+36°3639 discovered by Professor Campbell some 

 years ago. Direct photographs show a nebulous appendage about 4" 

 in diameter somewhat eccentrically situated in reference to the star. 



Miscellaneous. 



The spectra of several stars of very low luminosity have been photo- 

 graphed during the year. All of these, with a single exception, have 

 proved to be of types K5 to Mb. The exception is the comparison 



