Astronomy, 471 



Dotjghtyite, described by W. P. Headden, is a hydrated basic 

 sulphate of aluminium occurring as a white precipitate in connec- 

 tion with some of the Doughty Springs in Delta County, Colo- 

 rado. The composition of the air-dried material is given by the 

 formula: Al,(S0 4 ),.5Al„(OH) 6 .2lH s O. — Proc. Colo. Sci. Soc. y 

 viii, 66. 



III. Astronomy. 



1. Parallax Investigation of 162 Stars, Mainly of Large 

 Proper Motion. Transactions of the Astronomical Observatory 

 of Yale University : Volume II, Part I, pp. 207, Folio. Pub- 

 lished by Frederick L. Chase, Mason F. Smith and Wm. L. 

 Elkin. — The results of Dr. Elkin's work with the Repsold Helio- 

 meter on the parallax of 10 first magnitude stars of the northern 

 heavens were published in 1902, as Part VI of vol. I of these 

 Transactions. It may be noted here that nine of these stars have 

 a reliable parallax, varying from 0'02" to 0*33 ", and it is somewhat 

 significant that two of the three of inconsiderable parallax have 

 also inappreciable proper motion, while the seven remaining have 

 noticeably large proper motion, varying from 0-20" to 2*29", while 

 the average parallax of O'll" represents a distance of 29 light- 

 years. 



During the progress of this work, which together with the 

 triangulation of the Pleiades and that of the Group in -Coma 

 Berenicis by Dr. Chase had demonstrated the capacity both of 

 these observers and their instrument for the highest order of 

 parallax work, plans were formed for an investigation of all the 

 stars of known large proper motion across the line of vision con- 

 venient for observation (designated rather loosely in the report 

 as "all the rapid moving stars"). This work has developed in 

 the course of its prosecution so far beyond the limits anticipated 

 that it has occupied the larger part of the time of Dr. Chase for 

 13 years, Dr. Elkin having been interrupted by ill health and 

 largely occupied by work in meteorite photography. It has also 

 enlisted the services of Mr. M. F. Smith since 1901. 



By 1895 about 100 stars had been measured at two epochs of 

 greatest parallax effect, the original design being to detect paral- 

 lax without attempting the fullest determination of its magni- 

 tude, but the discussion of these measurements promised such 

 valuable results that it was decided to both enlarge and intensify 

 the work by including more stars and extending the measure- 

 ments over four periods, the last two being taken in reverse 

 order, as well to eliminate more completely the effect of proper 

 motion as to guard against the effect of systematic error which 

 might possibly be considerable in a limited number of observa- 

 tions. 



The precautions taken against systematic errors, whether 

 resulting from habits of observation, direction of comparison 

 stars or difference in their color or brightness, as well as from 



