42 



ON THE ORBIT AND PHENOMENA 



spherical triangle P F K, the longitude of F corresponding to its latitude as given 

 by the foregoing formulse, and if the difference between the two determinations 

 amounted to 2" (as it sometimes did, when the azimuth of the line of observation 

 was nearly coincident with that of the meteor's path), the arc G D was subdivided, 

 thus reducing the size of the trapezoid G N D M, and the consequent error. Also, 

 from this same triangle the arc jP/fwas computed. 



The heights of the meteor (column 14th), for the different positions of F, were 

 readily obtained by proportional parts from- the 5th column of Table 1st, and the 

 mean time at Washington was obtained, in the same way, from the 9 th column of 

 that table, which, corrected for the difference of longitude, gave the local time 

 (column 15th). 



The altitude and parallax of the meteor, at the several points (columns 8th and 

 11th) were computed thus: Let G in the following dia- 

 gram represent the centre of the earth, M the meteor, K 

 the place of observation, H K the sensible horizon, K F O 

 the vertical circle in whose plane the altitude M K Hwas 

 measured, and K F an arc of the same, as in the preced- 

 ing diagram. Then in. the plane triangle K M G, the sides 

 K G and M G being known, and also the angle at C, 

 since it is measured by the arc K F, already found, the 

 angles at M and K were readily found, the former of which 

 is the parallax, and the latter, diminished by the right 

 angle H K G, gave the altitude. 



