2 ON THEORBITAND PHENOMENA 



card to correspond. The angle included between the lines being then measured by 

 an ordinary protractor showed the co-altitude of the meteor. All the estimates of 

 this character were made several weeks after the date of the meteor's appearance, 

 when the vividness of the first impression may be supposed to have in some mea- 

 sure faded from the mind, and must of course be less reliable than observations 

 made under favorable circumstances at the time. Some of them gave positions for 

 the meteor so widely at variance with those deduced from more reliable observations 

 that it was thought better not to include them in the tabular series (Table II), at the 

 end of this memoir, in which the results of calculation are compared with those of 

 observation. The numbers affixed below to the names of most of the places at 

 which the observations were made refer to the aforesaid table. 



Description of the Observations and Remarks tliereon, the Names of the Places being 

 Arranged in Aljjhahetical Order. 



Achiever (schooner), Lat. 37° 10', Lon. 73° 15'. Capt. Knowles reports that the 

 meteor " rose in the west and passed to the E.N.E." ^ 



Albany, New York, Nos. 34 and 141. Observed by Prof O. M. Mitchell, who 

 says : " The meteor of July 20th, as seen by me, passed the meridian about 2° or 

 3° below Antares. It passed under Mars at about an equal distance," and that it 

 disappeared at an altitude of 8° or 10°. Prof E. Emmons says that it " had an 

 elevation of 12°," "measured by a theodolite and a known object observed at the 

 time it passed," and that it passed a little below Mars. The latter observation is 

 confirmed also by Amos Fish. 



Alexandria, Virginia, Nos. 4, 44, 63 and 103. The following extracts are taken 

 from an article written by Caleb S. Hallowell, Principal of the Alexandria High 

 School, dated July 24th, 1860, and published in the Alexandria Gazette: "The 

 most reliable observers here represent this interesting body to have appeared in 

 the northwest, at an azimuth of 20°, and an altitude of 10°; the first intimation 

 of its approach having been the lighting up of a small cloud, from which the 

 meteor shot out toward the east, in a nearly horizontal direction. By the time 

 it had attained an eastern azimuth of 3°,^ it burst or divided • into two bodies, dis- 

 tant from each other about half a degree. The foremost of these bodies was 

 somewhat the larger and brighter, and dis^Dlayed yellow light, Avhile the hinder 

 was tinged with a pale greenish-blue. The two proceeded onward, retaining their 

 relative positions, like birds flying through the air, hesitating, as it were, for a 

 moment, and then immediately moving onward with a slightly accelerated velocity. 



"By the time they had an eastern azimuth of 11°, their altitude had diminished 

 to 9°, and about this time occasional sparks were seen dropping back from the front 

 to the hinder ball, as though the body were in a process of combustion. Each ball. 



' According to the computed orbit, the altitude at the latter azimuth must have heen about 8° 

 the maximum altitude about 9°, and the former azimuth a mistake. 



" The calculated path shows a change of direction at Lat. 42° 18' 15", and Lon. 76° 42' 53", and 

 if the meteor burst at that point the true azimuth was N. 3° 15' 41" E. 



