F. A. Genth — Contributions to Mineralogy, 47 



becomes perpendicular to the line of sight the Bpectral lines 

 recover their true wave-length and become single. An idea 

 •1h> actual dimensions of the system may be derived from 

 the measures given above. The relative velocity as derived 

 from the K line will be 0*199 divided by its wave-length 393*7 

 and multiplied by the velocity of light 186,000, which is equal 

 to 94 miles a second. A similar calculation for the line whose 

 wave-length is 448- 1 gives 102 miles per second. Since the 

 plates were probably not taken at the exact time of maximum 

 velocity these values should he somewhat increased. We may 

 however assume this velocity to be about one hundred miles 

 per second. If the orbit is circular and its plane passes 

 through the sun, the distance traveled by one component of 

 the star regarding the other as fixed would be 900 million 

 miles, and the distance apart of the two components would be 

 143 million miles, or about that of Mars and the sun. The 

 combined mass would be about forty times that of the sun 

 to give the required period. In other words, if two stars each 

 having a mass twenty times that of the sun revolved around 

 each other at a distance equal to that of the sun and Mars, 

 the observed phenomenon of the periodic doubling of the lines 

 would occur. If the orbit was inclined to the line of sight 

 its dimensions and the corresponding masses would be in- 

 creased. An ellipticity of the orbit would be indicated by 

 variations in the amount of the separation of the lines, which 

 will be considered hereafter. The angular distance between 

 the components is probably too small to be detected by direct 

 observation. The greatest separation may be about 1*5 times 

 the annual parallax. Some other stars indicate a similar pecu- 

 liarity of spectrum, but in no case is this as yet established. 



Addendum, Dec. 17. — The predicted doubling of the lines of 

 * Ursae Majoris on December 8th was confirmed on that day by 

 rach of three photographs. Two more stars have been found 

 showing a similar periodicity : ft Auriga? and b Ophiuchi (H. P. 

 1100 and 2909). 



Harvard College Observatory, Cambridge. U. S., Nov. 12, 1889. 



Art. IX — Contributions to Mineralogy, No. 40 ; by 



F. A. Genth. 



On a new occurrence of Corundum, hi Patrick Co., Vcl 



In the fall of 1888, Mr. W. B. Pucker, of Stuart. Patrick 

 County, Va., discovered a highly interesting occurrence of co- 

 rundum, and kindly communicated the following details of his 

 find and the locality, and presented me with a box of speci- 

 mens for examination, consisting of corundum with its associ- 



