146 Mr Harvey on a Luminous Arch seen at Plymouth. 



Art. XXII. — On a splendid Luminous Arch seen at Plymouth, 

 Sept. 29, 1828. By George Harvey, Esq. F. R. S. Lond. 

 and Edin.j F. L. S., F. G. S., &c. &c. Communicated by the 

 Author. 



At 10 minutes after 8 p. m. on the day above mentioned, a 

 column of white light, about 20"" above the horizon, 20° long, 

 and about 1° wide, was perceived in the W. S. W. quarter of 

 the heavens. The appearance was unusual, but still not such 

 as to arrest particularly the attention. After an interval of 5 

 minutes, its extent had very much increased, appearing with 

 extraordinary splendour between a Lyrae and a Aquilae, and 

 crossing the meridian about 10° to the south of a Cygni, its 

 breadth at the same time being doubled. Hastening to higher 

 ground, to command more completely the beautiful pheno- 

 menon, it was found, at 27 minutes after 8, to extend across the 

 heavens, passing nearly midway between /3 and y Andromedae, 

 covering with its pure and delicate light the Pleiades, and de- 

 spending nearly to the eastern side of the horizon. During the 

 changes, the western portion of the arch increased also in 

 length, descending to within 10° of the horizon, where it was 

 obscured by clouds ; and at the same time, it was observed to 

 undergo a remarkable inflexion towards the north, at about the 

 elevation of /3 Ophiuchi, over which star it passed. 



.^h^ whole arch now presented one magnificent zone of clear, 

 white, silvery light, of about 4° wide, having its edges parallel, 

 and beautifuUy^ defined. Its general direction, independently 

 of tlie iufles;io^, was nparly in the plane of the dipping-needle; 

 and but for that inflexion, its two extremities would have been 

 in a line at right angles nearly to the magnetic meridian. 



The brightness of the arch was by far the greatest at its 

 western extremity, the light progressively diminishing to its 

 eastern end. The light also was steady, presenting no corus- 

 cations, excepting at about 20 minutes before 9, when a 

 trembling about the Pleiades was perceptible, the arch in that 

 region appearing to separate into somewhat indistinct laminae, 

 from north to south, at inclinations of about 40°. 



As the growth of the arch from west to east, was accompa- 



