474 Scientific Intelligence. 



to the form and extent of calcium flocculi at various elevations 

 above the photosphere, to dark calcium flocculi, and to hydrogen 

 flocculi. The text is admirably illustrated by fifteen beautiful 

 full-page plates reproducing the original negatives of faculae, 

 flocculi, sun-spots, etc. 



Part II is entitled "The Spectrum of the High Potential 

 Discharge between Metallic Electrodes in Liquids and in Gases 

 at High Pressures, ' ' by George E. Hale and Norton A. Kent. 

 For lack of space, it is not possible to do justice to this valuable 

 contribution to spectroscopy. Suffice it to say that, in general, 

 the spark lines from iron electrodes in water and in solutions 

 of sodium chloride are broadened and greatly reversed as com- 

 pared with the spectrum in air at standard pressure. The lines 

 produced under water are also much weakened and reversed by 

 increasing the self-induction in the circuit. In air and carbon 

 dioxide the lines are reversed and shifted toward the red by 

 increasing the gas pressure. In general, for the same line, the 

 shift is directly proportional to the increase in pressure. The 

 graphs corresponding to lines of the same spectral type have 

 equal slopes. The descriptive matter of Part II is illustrated 

 by eight plates of the same degree of excellence as characterizes 

 those of Part I. 



Volume IV, Part I (1917) has the title Stellar Parallaxes 

 Derived from Photographs Made with the Forty-Inch Refractor. 

 It contains the following papers : An introductory note by the 

 Director, Edwin B. Frost ; parallaxes of forty-two stars, by 

 Frederick Slocum and S. Alfred Mitchell ; parallaxes of seven- 

 teen stars, by Oliver J. Lee and Alfred H. Joy; parallaxes of 

 twenty-six stars, by Lee aild Georges Van Biesbroeck; index of 

 parallaxes for 131 stars; an appendix on the investigation of a 

 new screw measuring machine at the Yerkes Observatory, by 

 Lee and Hannah B. Steele ; and two full-page plates, h. s. u. 



6. Axial Aberrations of Lenses. — In a recent paper by E. D. 

 Tillyer and H. I. Shultz an account is given of the results of 

 an investigation which was undertaken to determine the errors 

 of a complex lens system that affect the definition of the image 

 near the center of the field, and to compare the different types 

 of lenses on the market with respect to their corrections for 

 central definition and their applicability to the various purposes 

 for which they might be used. The lenses studied fall under the 

 following principal classes: Photographic lenses of relatively 

 large aperture; projection lenses for stereopticon and motion 

 picture work; telescope lenses of short focal length and large 

 aperture, and telescopic systems. Hartmann's method has been 

 extended so that it is now possible to obtain from one set of 

 measurements the data for all the important central errors, 

 which are — spherical aberration, zonal variation of the equiva- 

 lent focal length, and axial and oblique departures from achro- 

 matism. The results of the method as applied to a complete 



