192 REPORTS ON INVESTIGATIONS AND PROJECTS. 



divisions later than in the Harvard catalogue. The stars with hazy lines are 

 in good agreement throughout. 



Miscellaneous Stellar Spectra. 



The spectra of 25 faint stars down to mag. 11.3 were obtained by Mr. 

 Fath. A number of these were long-period Algol and ft Lyra? type variables. 

 It was thought that possibly these long-period variables might be of a dif- 

 ferent type from those of short period, but those investigated all show an 

 early type spectrum, either B or A. With the small dispersion used these 

 types can not be differentiated. Fifteen plates containing the spectra of 36 

 stars were taken by Mr. Fath with the quartz spectrograph. The stars were 

 selected in such a way that on any one plate they should be of the same 

 spectral type and magnitude but have very different proper-motions. It was 

 expected that on the average the stars of small proper-motion, being farther 

 away than those of large proper-motion, would show less density in the 

 ultra-violet portion of the spectrum. The evidence from the plates, how- 

 ever, is not conclusive. 



Spectra of Nebulae and Globular Clusters. 



The spectrum of the spiral nebula N. G. C. 4826 was photographed by Mr. 

 Fath, with an exposure of i6 h 15" 1 . The plate, though somewhat under- 

 exposed, shows that the type of spectrum is analogous to that of the sun. 

 The spectrum of the great star-cluster in Hercules, N. G. C. 6205, was also 

 photographed with a total exposure of I5 h 35 m . The negative is of good 

 density and indicates that the cluster is composed largely of F and G type 

 stars, the F type probably being more numerous. 



MAGNETIC FIELD OF NEBULAE- 



Rotating charged bodies, such as we may suppose planetary and spiral 

 nebulae to be, should presumably give rise to a magnetic field the poles of 

 which correspond approximately with the poles of rotation. Although it is 

 very doubtful whether these fields can be detected with existing instru- 

 ments, the Director and Mr. Babcock thought it worth while to make the 

 attempt, as the 60-inch reflector is well adapted for the purpose. The ob- 

 ject chosen in the first instance was the bright planetary nebula N. G. C. 

 6543. An exposure of 3^ hours with a Fabry and Perot interferometer, 

 mounted with collimator, camera, and right and left handed circular ana- 

 lyzers in the new steel frame of the concave grating stellar spectrograph, 

 failed to show any trace of interference fringes. We therefore decided to 

 use a 33-plate echelon, mounted with auxiliary spectroscope on the inclined 

 pier south of the 60-inch reflector, its axis coinciding with the polar axis of 

 the telescope and its slit in the focal plane of the coude combination of 150 

 feet focal length. The analyzing apparatus, suggested by Mr. Babcock, con- 

 sisted of a half-wave plate covering half of the slit, and a quarter-wave plate, 



