REPORT AND JOURNAL. 147 



light and no one stirring- in camp, 1 began to think that the cooks had not been called 

 by the guard, and that we were likely to have a late start for the day. Taking up my 

 watch, which was lying on the table near me, I could distinctly read on its metallic 

 face the time of the night, and, to my surprise, found it was only 11 o'clock. Before 

 I went to bed, about 9 o'clock, the moon had set, and 1 recollected that it was with 

 some difficulty I had been able to discern the figures of a couple of my assistants who 

 were taking astronomical observations, though they were not far from me. These 

 facts were curious, and I leaped to the front of my tent to clear up the matter. As 

 soon as I looked out the anomaly was explained. About two-thirds of the whole 

 southern celestial concave was one sheet of beautiful roseate light. 



"For a while the light continued in a state of repose, the most concentrated portion 

 forming a belt, and extending from a point on the horizon a few degrees north of east 

 (about 10) clear across the heavens to a point on the horizon about due west. From 

 this belt the light, with its roseate hue, was diffused southwardly all over the heavens, 

 with' marked distinctness, down to the arc of a circle, the angle of wla.se plane with 

 the horizon was about 10 degrees. 



"For a period, as stated, the phase of the phenomenon appeared constant; it then 

 changed gradually, alternately varying to a less or greater intensity, the rosy light 

 still remaining diffused. At length, however, the light assumed a more intense form 

 and shot up in whitish coruscations from the base or lower limit of the illuminated 

 portion to the apex or crown, which was about 20° to the south of the zenith; the 

 appearance of the concave all this while being that of an illuminated globe divided 

 into an innumerable number of meridians, and the vanishing-point or apparent pole 

 the apex referred to. 



"At the time of the phenomenon, I observed the magnetic needle, but could not 

 perceive that it was sensibly affected by it. It being, however, only a pocket one, it 

 could not, of course, be capable of expressing any but very large perturbations. 



"The phenomenon was so extraordinary and beautiful that I called up my assist- 

 ants to observe it. It then appeared that one of them (Mr. Jagiello) had observed it 

 at 10 o'clock, and, as it disappeared about 12, it must have lasted about 2 hours. 



"The aurora borealis, as seen north of the zenith, is a phenomenon of frequent 

 occurrence ; but a southern illumination, like that I have described, I have never 

 before seen, and I leave it to those who are familiar with such subjects to explain the 

 cause.* 



"I am, very respectfully, your obedient servant, 



"J. H. Simpson, 

 "Captain Corps Topographical Engineers. 



" Professor Joseph Henry, LL. D., 



" Secretary of Smithsonian Institution, Washington, I). C." 



* I have received the following reply to this letter from Professor Henry : 



"Smithsonian Institution. Washington, D. C, October 25, 1859. 



"Dear Sir: I write to thank you for your very interesting letter relative to the aurora borealis of the 1st of 

 September, which is important, particularly on account of its locality and the precision with wh.ch you have de- 

 scribed the phenomena. 



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