1889.] On the Spectra of Meteor-swarms. 385 



present I have no means of doing this myself. The stars selected for 

 observation were a few of the brightest hitherto known as belonging 

 to Class II& of Vogel's classification. A few stars more advanced than 

 the II& stars and a few less advanced were also observed in order that 

 the passage from one group to the other might be determined. 



The main points to which attention was directed were (1) the 

 relative intensities of F, 6, E, D, both in the same star and from star 

 to star ; (2) the lines which appear to be special to one group or the 

 other (III or V). 



The importance of observing the thickness of F in the spectrum of 

 a star, as compared with its thickness in other stars, is obvious, for it 

 at once enables us to fix the position of the star on the temperature 

 curve immediately we have determined whether its temperature is 

 increasing or decreasing. 



Details of the observations of the thirteen stars which appear to be 

 on the ascending side of the temperature curve are given below. One 

 of these is a Group IV star, and one is a swarm of the last species of 

 Group II. The remainder belong to Group III. 



The stars are arranged in order of temperature, beginning with the 

 lowest, as far as the observations enable us to do this. In general, 

 the observations have been limited to the region of the spectrum 

 lying between F and the iron fluting in the red at wave-length 615. 



The wave-lengths of the lines and flutings were determined by 

 direct comparison with the electric spark, and with the lines and 

 flutings seen when the various substances are volatilised in the 

 Bunsen burner. On one or two occasions, comparisons were also 

 made with the spectrum of the Moon. 



at. Ceti. F is fairly well seen, but it is not nearly so thick as b or 

 D, and not quite as thick as E. D is pretty thick and lies in the 

 Mn (2) fluting (586). b is also thick. The trio of lines* in the 

 green is present, the most refrangible member being the darkest. 

 Lines are present at about 579 and 568'5, the former being the stronger. 

 Lines at 499 and 552 rather thin. The absorption Fe (1) fluting at 

 615 and Mn (2) are both present, but far less intense than in Mira 

 Ceti, The flutings Mn (1) 558 and Pb (1) 546, are also both feebly 

 visible. The brightest fluting of carbon at 517 is just perceptible. 

 This is therefore a very late star of Group II. It is, in fact, the mos.t 

 advanced Group II star of which observations have at present been 

 made. 



i Aurigce. Spectrum greatly resembles that of Aldebaran. F is 

 thin. D is very thick, and more prominent than b. The trio of lines 

 in the green is weJ seen. 579, 568, and the lines near 546'5 and 558 

 are well seen. The lines at 499 and 552 are also present. The iron 



* The trio referred to in the observations comprises the lines E (5268), 5327, 

 540. 



