On the Necessity of Animal Decay. 423 



fiavc shone directly over the Pointers, and also over the Vleiarles; 

 the zenith distance of the top of the arch hehoved therefore to 

 he 5° or 6'" (sxippose 3° 30') to the northward: — let this he added 

 to 45° 30', the zenith distance here, the sum is 5 1°. If from this 

 sum we subtract 1" AT, the difference of latitude hetween Glas- 

 gow 55'^ 51', and Gordon Castle 57° 3S', the remainder 49' 13' 

 is the angle subtended by the distance of Gordon Castle from 

 Glasgow; — this distance by Arrowsniith's Map is about 128 

 miles. 



From these data, calculating by plane trigonometry, the highest 

 part of the arch appears to have been distant from Gordon Cas- 

 tle I68i miles; and from Glasgow 118y miles, its least distance 

 from the earth; consequently not quite 118 miles. 



Another very luminous arch of this kind appeared here on the 

 5th of February last, at 8'' 20™ P.M. When it was first observed, 

 its breadth was about one degree ; both ends of it reached nearly 

 to the horizon, a little to the N. of E. and to the S. of W. Its 

 upper edge passed about 5° to the south of the star Capella, 

 touching the most southerly of the Two Kids. To the westward 

 the arch was parallel to the two brightest stars in Aries, and 

 at the distance of its own breadth, or one degree below them. 

 The zenith distance of the top of the arch was consequently about 

 14° towards the south. At half past eight o'clock, the middle 

 part of the arch and Capella were obscured by clouds; the 

 western part had become faint, and p. little further separate from 

 the stars in Aries; the eastern half was still bright, and had 

 moved considerably northward. At 8" 50"" it was all gone. 



If any of the numerous readers of The Philosophical Magazine 

 shall have happened to see either of these two phenomena, and 

 to have made similar observations of them, it would be desirable 

 if they would send them to you to be published, that they might 

 either confirm or correct the foregoing result ; and afford moans 

 for determining whether these arches of the aurora borealis are 

 generally at the same distance from the earth ; or whether there 

 are not considerable differences in their heights at different 

 times. I am, &;c. 



Gordon Castle, May 13, 181 8. JamES Hoy. 



LXXII. On the Necessity of Animal Decay, 



To Mr. Tilloch. 



Sir, — ' Among the reasons usually given for the necessary de- 

 cay and dissolution of animals and other organized bodies, is 

 there any one that will bear the test of accurate examination ? 



Dd4 If 



