38 



SCIENCE 



[N. S. Vol. XXXVII. No. 940 



can be aecoimted for by the orbital motion of the 

 binary. Assuming the effective light center of 

 AB to be one seventh of the distance from A 

 toward B, he determines the mass ratio of the 

 binary to be m'/m = 0.9. 



Within the next five years the radial velocity 

 will again reach both maximum and minimum 

 values, and spectrographic observation during this 

 interval will be of the greatest value in deter- 

 mining the orbit elements more precisely. 



International Standards of Wave-lengths: C. E. 



St. John and L. W. Waee. 



This paper, which has appeared in full in the 

 Contributions from the Mount Wilson Solar Ob- 

 servatory, No. 61, gives the results of the measure- 

 ments of two series of plates of the iron arc 

 spectrum, obtained with two plane grating spec- 

 trographs, one on Mt. Wilson and one in Pasadena. 

 The precision obtained by interpolation between 

 the international standards of the second order is 

 0.001 Angstrom in the case of good lines. No 

 errors were found in the relative wave-lengths of 

 the secondary standards between X5371 and X6494 

 greater than 0.001 Angstrom except for the line 

 X5434, where it is 0.002 A. In this region 44 lines 

 were found unsuitable for standards of wave- 

 lengths on account of pressure displacements 

 accompanied with dissymmetry. Several lines 

 showed differences in wave-length between the 

 two series, bearing relation to the quality of line 

 under pressure as shown on the plates of Gale 

 and Adams. 



The Solar Rotation: J. S. Plaskett. 



This paper presents the general results of a 

 determination of the solar rotation for 1911 and 

 a preliminary result for 1912. The values ob- 

 tained at Ottawa for 1911 are well represented by 

 the formula 



vz= (1.483 + 0.532 cos= <p) cos <t>, 

 | = 10°.32 + 4°.05 cos <t>, 

 where v is the sidereal linear velocity of the re- 

 versing layer in km. per sec, and J the daily 

 sid-^real angular velocity, the solar latitude. 

 These are in remarkably good agreement with 

 Duner's and Adams's 1908 values, except for a 

 small angular difference constant for all latitudes. 

 The formulas probably represent very closely the 

 law of variation with latitude. Measures of the 

 same plates by different observers give systematic 

 differences of two or three per cent., indicating 

 that the differences noted above are probably per- 

 sonal, and due to the character of the lines. The 



discussion of some 3,000 residuals from different 

 lines and elements show no systematic differences 

 of velocity for different elements, or for different 

 lines of the same element. No change greater 

 than one per cent, is revealed in results for 1911 

 and 1912. 



The Spectroscopic System 9 Camelopardalis : O. J. 



Lee. 



This star was announced as a binary by Frost 

 and Adams" from measures of the broad lines. 

 They also found that the H and K lines, strong 

 and narrow, give a variation which differs in 

 phase and amplitude from that given by the other 

 lines. 



The observations cover about 3,000 days. The 

 form of the velocity curve is incompatible with a 

 simple two -body system and hence a certain form 

 of calcium envelope has been assumed which both 

 assists in reproducing the observed velocity curve 

 and accounts for the difference in character of the 

 broad lines and the calcium lines in the spectrum. 

 The observed velocity curve is composed of three . 

 elements : the orbital velocity of the primary, the 

 velocity of the calcium envelope about the center 

 of the primary regarded as a stationary point, and 

 the periodic eclipse of the spectroscopieally ef- 

 fective parts of the envelope by the primary. 



The elements of the stellar orbit are: P = 

 7.9957 days, e = 0.30, ^ = 45°.024, ir = 9.0, m = 

 90° or 270° closely, 2' = J.D. 2,416,480.35, y = 

 — 2.25 km., 1^90° nearly. 



Assuming that the effective calcium clouds cen- 

 ter about the two zero velocity points, which lie 

 one on each side of the primary M/in = 2.85 and 

 M -f m = 0.0023. 



The Eotation of Jupiter's First Satellite: A. E. 



Douglass. 



This satellite appears ellijitical in form. A 

 number of persons unacquainted with the identity 

 of the satellites have been asked to select the one 

 appearing elliptical. In fourteen out of seventeen 

 trials the first has been picked out. The ellipticity 

 is not constant, but varies on a period which does 

 not seem to be constant. A hypothesis to account 

 for the phenomena supposes the satellite to be an 

 irregular body resembling an ellipsoid of three 

 unequal axes in which the axis of figure has a con- 

 siderable angle to the axis of rotation. 



The Light-curve of SS Cygni from the Amherst 

 Observations: D. P. Todd and C. J. Hudson. 

 Observations of this star and about 50 other 



^ Ap. J., 19, 350, 1904. 



