156 



SCIENCE 



[N. S. Vol. XXIX. No. 734 



April 2, 1907, and September 11, 1908. The 

 emulsions used were Seed 27, Seed 23 and lantern 

 slide. The lines K, H5, H7, X 4481 and H;3 were 

 the only ones measured. On the lantern slide 

 and Seed 23 plates numerous other faint lines 

 were visible, and in some cases measurable, but 

 were not used. Among them are the lines X 4128 

 (silicon), X 4227 (calcium), X 4233 (iron), X 4352 

 (magnesium), X 4472 (helium), X 4550 (iron). 

 A dozen other lines could be approximately lo- 

 cated, while still others were occasionally faintly 

 visible. 



Mr. Jordan found that the total range in 

 velocity is 69.86 km. As the periastron point is 

 in the fourth quadrant, the ascending branch of 

 the velocity curve is steeper than the descending. 

 The center of gravity of the system has practi- 

 cally no velocity in the line of sight. 



No trace of a secondary spectrum can be seen. 



9. In No. 604 of the Astronomical Journal, pub- 

 lished on September 25, 1908, Professor Lewis 

 Boss communicated an important paper entitled 

 " Convergent of a Moving Cluster in Taurus." 

 In this he presents the evidence, derived from 

 their proper motions, that 39 stars in or near 

 the Hyades are converging upon the same point. 

 Radial velocities have been published by Kustner 

 for three stars of the cluster, namely, 7, S and 

 e Tauri. Assuming these values to be representa- 

 tive of the cluster, the radial velocities of the 

 remaining stars can be inferred. They would 

 range from 37 to 44 km. per second. Before the 

 article was printed Professor Boss had privately 

 called the attention of Professor Prost to his 

 results and to the desirability, in so far as pos- 

 sible, of determining the 'radial velocities of the 

 stars in the cluster. He accordingly added the 41 

 stars to the observing program of the spectro- 

 graph, and during the present autumn they have 

 been observed, as circumstances permitted, chiefly 

 oy Messrs. Barrett and Lee. 



The spectra of most of the stars are of the first 

 type, so that the lines are generally diffuse and 

 suitable for only the dispersion of the single 

 prism which has been regularly employed for 

 them. 



There has not yet been opportunity to measure 

 these plates and this note is merely given to state 

 that this piece of work is in progress. Thus far 

 60 spectrograms have been obtained of 21 of the 

 stars, the magnitude of which are mostly between 

 4.5 and 5.6. 



It may be said from a preliminary examination 

 of the plates that no star contradicts in sense the 

 value presumptive from Professor Boss's re- 



searches, and in general the radial velocity ap- 

 pears to be of about the amount expected. Some 

 of the spectra will hardly admit of accurate 

 enough measurement to establish the accordance 

 with the predicted values. This examination only 

 indicates that the stars thus far observed are 

 receding from the sun with velocities of about 

 40 km. per second. No inference can yet be 

 reached as to the diflferenees in radial velocity 

 dependent upon the star's position in relation to 

 the point; of convergence. 



We have been somewhat surprised at the large 

 proportion of spectroscopic binaries already de- 

 tected in this cluster. Six of those so far ob- 

 served appear to be certainly of this character, 

 and others are suspected. 



The six are: 90 Tauri and B.D. 15°.637, found 

 by Mr. Barrett; 6Jf Tauri and 97 Tauri, found by 

 Mr. Lee; S' Tauri and 69 (Upsilon) Tauri, found 

 by the writer. The last two had been observed 

 before Professor Boss called attention to the 

 cluster. 6- Tauri has also been detected as a 

 speetroseopie binary at the Lick Observatory. 

 Double lines are exhibited by the first ^ ro and 

 last three stars. 



10. The paper by Messrs. Fox and Abetti pre- 

 sents evidence proving occasional interaction of 

 sun-spots. On spectroheliograms obtained on Sep- 

 tember 10, 1908, regions surrounding three spot 

 groups then just past the central meridian were 

 observed to burst synchronously into active erup- 

 tion. The eruptions progressed until the interval 

 between the two larger groups, about 120,000 

 miles, was completely and brilliantly bridged. 

 The whole display lasted less than four hours. 

 Successive plates, shown by lantern slides, re- 

 vealed the progressive stages of the demonstration. 



11. It is known that on the Riemann surface 

 associated with 



s=± VA(2: — Oi) (» — Oj) (ss — 03) (z — a^)■, 



in which a, and Oj are connected by a canal as 

 are also Qj and Oj, that every one-valued function 

 of position which has everywhere a definite value 

 is of the form 



to = p -|- g • s, 



where p and q are rational functions of the com- 

 plex variable e; and reciprocally every function 

 of the form 



w = p + q — s 



is a one-valued function of position on this Rie- 

 mann surface. If we denote two such functions by 



tOi = p, -{- gi . S, tCj = Pa + ^2 • s. 



