ASTRONOMY: F. G. PEASE 519 
made in such a way that the nebular spectrum was traversed longitu- 
dinally by comparison spectra at intervals of 1 mm. The photographic 
plate accordingly was used in its regular position, and thus a large part 
of the spectrum was in focus. 
N 
FIG. 3.— N. G. C. 4594 EXPOSURE = 2 HOURS. 1 MM = 6.7 
E 
W 
FIG 4.— SPECTRUM OF N. G. C. 4594. EXPOSURE 80 HOURS. 
The resulting spectrum (fig. 4) represents approximately the central 
half of the nebula, and it has been found possible to obtain measures 
in five spaces (2J minutes of arc) on either side of the nucleus. The type 
is about F5 and seems to be alike in all parts of this nebula. The 
linear scale of the spectrum is 4.3 mm. from X 3930 to X 4950 and most 
