Aurora Bofealis of November 14, 1837. ■ 289 



summit. Such also is that of Professor Joshii, who supposes 

 an intimate connection to exist between clouds of certain forms, 

 and auroral phenomena. But these seem to find little support in 

 mathematical computation, founded on the observation of par- 

 allax, "^ ri:c. 



During the expedition of Capt. Franklin to the polar regions, 

 however, in 1820, contemporaneous observations were made on 

 three Auroras, by Lieutenant Hood and Dr. Richardson, in latitude 

 64° 2' 24'^, from points eighteen leagues distant from each other ; 

 and from the parallactic angles obtained by them, an altitude was 

 deduced of two or two and a quarter leagues — equal to six or 

 seven English miles. It is possible that the height may diminish 

 as we approach the poles. 



According to the theory of M. Hansteen, the auroral cloud is 

 an emanation from the earth, which rises directly upward, but 

 becomes luminous only on escaping from the atmosphere, at a 

 height of forty five or fifty miles. 



But there have been differences of opinion in regard to the ori- 

 gin of the auroral vapor^ as to whether it is terrestrial or celestial. 

 That it partakes of the motion of the earth, in its diurnal revolu- 

 tion, is sufficiently evident. Whether this fact alone will demon- 

 strate it to be a terrestrial emanation, may possibly be disputed; 

 but it is certainly an argument in favor of that belief. 



The Aurora has been represented to be attended with rustling 

 or crackling noises. In our latitude we have no very good evi- 

 dence of the occurrence of these : and, indeed, if the auroral va- 

 por be, in truth situated as far above the earth as our computations 

 as yet compel us to place it, we know not how such audible evi- 

 dences of its action can reasonably be expected. The case would 

 be somewhat different, if the sounds described were heavy peals 

 or explosions, like the reverberations of thunder. These sounds 

 are represented as being more remarkable, and of more frequent oc- 

 currence in the higher latitudes. This circumstance might result 

 from the more violent action of the Aurora, as we approach the 

 poles ; but it may, also, be in part, a consequence of the greater 

 proximity of the phenomenon to the earth's surface. M. Mairan, 

 believing the auroral matter to ascend from the earth, and during 

 a coronal Aurora, from the immediate region of the observer, sup- 

 poses these sounds to be occasioned by its upward passage through 

 the lower regions of the atmosphere. 



YoL. XXXIV.— No. 2. 37 



