TRANSIT OF VENUS, DECEMBER 6, 1882. 509 



OTHER PUBLICATIONS RECEIVED. 



Frontier Army Sketches, by Capt. James W, Steele, Jansen, McClurg & Co. , 

 Chicago, $1.50; Jewish Nature Worship, by J. P. MacLean, Robert Clarke & 

 ■Co., Cincinnati, Ohio, 25c; Geological Sketches, Archibald Geike, LL.D., F. 

 R. S.; Humloldt Library, No. 38, 15c; Paper-Money Inflation in France, by An- 

 drew D. White, roc; The Gulf Stream, by Commander J. R. Bartlett, U. S. N.j 

 The Change of Life in Health and Disease, by Edward John Tilt, M. D., P. 

 Blakiston, Son & Co., 75c; Results of Meteorological Observations made in Hen- 

 ry County, Indiana, from 1854 to 1882, by Wm. Dawson. 



SCIENTIFIC MISCELLANY. 



TRANSIT OF VENUS, DECEMBER 6, 1882. 



W. W. ALEXANDER, KANSAS CITY. 



The Kansas City mean time of Internal Contact at ingress, December 6th, 

 '8h. 04m. A. M. Internal Contact at egress, December 6th, ih. 30m. P. M. 

 Apparent diameter of Venus 64.6", of the Sun 1952.4". 



Determination of the Sun's Distance. — We all know when Venus crosses 

 the Sun's disc during its transit it appears as a round black spot, (about one-thirtieth 

 of the Sun's diameter). Let us suppose two observers placed at two different 

 stations on the Earth, properly chosen for observation of the phenomenon; one 

 at a station in the northern hemisphere, another at a station in the southern hem- 

 isphere. When Venus is exactly between the Sun and the Earth, the observer at 

 the northern station will see her projected on the Sun ; the southern observer from 

 his lower station will see her projected higher on the disc of the Sun. Now, 

 what we require to know, in order to determine the Sun's distance, is the dis- 

 tance between the lines ? 



~ If the distance between the two stations is sufficiently great, the planet will 

 not appear to enter on the Sun's disc at the same absolute moment of time at 

 the two stations, and therefore the paths traversed, or the "chords," will not be 

 the same. Speaking generally, the chords will be of unequal length, so that the 

 time of transit at one station will be different from the time at the other. This 

 difference will enable, us to determine the difference in length of the chords de- 

 scribed by the planet, and consequently their respective positions on the solar 

 disc, and the amount of their separation. Now, this separation is what we want 

 to know. 



We already know the relative distances of Venus from the Earth and Sun; 

 they are as 28 to 72 nearly; and whatever the absolute distances may be, the 



