172 PIIOCEEDINGS OP THE AMERICAN ACADEMY 



the light were noticed), some of them are often omitted in Table X. 

 A few accidental omissions may also have occurrt3d. 



Table XI. contains results similar to those of Table X., taken from 

 the Zodlacallicht-Beobachtungen of Heis, to which reference is made 

 in the preceding discussion by the letter II. The first column of 

 Table XI. contains a continuous series of numbers, not taken from 

 Heis, but inserted here for convenience of reference. The second 

 column gives the name of the observer, and the third the date. The 

 next three columns give the longitude of the Sun, the latitude of the 

 observer, and the hour angle of the north pole of the ecliptic, denoted 

 by /, as in Table X., and found in the same manner. These col- 

 umns are followed by the elongation of the vertex, which is occa- 

 sionally given by Ileis in half-degrees, but here expi'essed in whole 

 degrees only. The last six columns give the latitudes of the northern 

 and southern boundaries at the elongations 30°, 60°, and 90°, as in 

 the case of the '' Stronger " Light of Jones. In the work of Heis, the 

 latitudes of the northern and southern boundaries are given at inter- 

 vals of 10° in longitude. The longitude of the vertex, as well as its 

 elongation, is also given. From these data the latitudes of Table XI. 

 have been obtained by estimate. Negative quantities are expi'essed 

 by Italic figures, as already explained in the description of Table X. 



Table XII. contains results derived from Schmidt's work, " Das 

 Zodiacallicht," designated as " S " in the preceding discussion. The 

 observations are here arranged in the order of the seasons, as they 

 were placed by Schmidt on pages 55-61 of his work. Besides the 

 observations there given, five others, made Dec. 1-20, have been col- 

 lected from the previous pages. Schmidt seems to regard them as too 

 uncertain to be worth reduction (.S. 54, 68), but it has been shown 

 above (p. 165) that they probably have a distinct meaning. 



The first three columns of Table XII. contain a number for refer- 

 ence, the date of the observation, and the latitude of the observer's 

 station. The next four columns give the zenith distance of the north 

 pole of the ecliptic (here called the inclination of the ecliptic for the 

 sake of brevity), the azimuth of the north pole of the ecliptic, the lon- 

 gitude of the Sun, and the elongation of the zenith, all derived from 

 Tables HI. to IX. inclusive. The last ten columns give the north 

 and south latitudes of the boundary of the light for the elongations 

 30°, 60°, 90, 120°, and 150°. They are derived from Schmidt's data 

 on pages 55-61 of his work, except that for the first five observations 

 a separate reduction was necessary. This was effected by means of 

 a chart like that just explained (p. 168). 



