VOL. XXXIV.] PHILOSOPHICAL TRANSACTIONS. 150 



might see the star's from under it to the north and south. The north side of 

 it I suppose first took fire, and shot its streams or flames perpendicularly up- 

 wards, which being undisturbed by winds, must appear straight and pointed at 

 the top. The bases must make an arch by the rules of perspective : for I think 

 a horizontal right line, of a vast length, and at a great distance from us, such 

 as I take the northern edge of this luminous cloud to have been, seen at a con- 

 siderable height in the air, must appear bent down into an arch. On a sudden 

 the fire propagated itself to all parts of this vapour. The whole heaven must 

 then appear covered with the same streams, which though really parallel to 

 each other, must appear bent into a cupola. The shooting and darting of these 

 flames, and their concourse, together with a smoke proceeding from them, 

 must give that confused cloud which was observed in the centre of this canopy. 

 I think the red appeared at the right hand in all of the colours, which were 

 regularly disposed in every stream. Somewhere in the Philos. Trans. I have 

 met with an observation of an aurora, in which the streams were coloured only 

 where they met, or crossed each other. Whether the light of one stream 

 passing through another, may not be separated into colours by refraction, I will 

 not determine. 



The same jJppearcmce described by John Hadley, Esq. F.R.S. N° 395, p. 146. 

 This description of the appearances is much the same as the preceding ones. 



The same Pheiiomenon observed at Geneva. By J. L. Calandrini, Professor of 

 Mathematics there. N° 395, p. 150. 



The description is much the same as the foregoing. M. Calandrini, in con- 

 clusion says : it is affirmed, that those northern lights are produced by the re- 

 flection of the sun's light from the northern frozen parts of the atmosphere ; 

 but he does not see how such remarkable flames can be explained. If this 

 phenomenon be supposed to arise from the accension of exhalations, the aurora 

 borealis that accompanies the phenomenon, the columns, the duration of the 

 appearance, and its continuing in the same place, will be the grand difficulty. 



jin jiccount of a Preternatural Bony Substance found in the Cavity of the 

 Thorax. By Mr. William Giffard, Surgeon: and a further Account of it, by 

 Dr. Rutty. N'' 395, p. 152. 



May the 10th, 1726, Mr. GifFard opened the body of a person who died of 

 a peripneumonia. In the right side of the thorax was found an osseous sub- 

 stance, about -^ of an inch thick, 6 inches long, and 3 broad, extending itself 



