BASAITES. 287 



fixed in the fcreen at the points of interfedionj which lines the heavenly 

 drawn from every point of the bodies to the eye of the ob- '"^'^'" '""ft a?- 



■' ^ pear largeft la 



ferver, make witii the fcreen. Now fuch a femi-tranfparent ^hehgriaan. 

 fcreen, the blue tkies inferpofe between the heavenly bodies 

 and our eyes. Tliey will therefore appear to be fixed in the 

 iky, at the above-mentioned points of interfedion. 



But if lines DC, H C, IC, BC, be drawn fo that the 

 angles at C are equal, they may be confidered as coming from 

 the extreme points of bodies which fubtend equal angles of 

 viilon, or which have the fame apparent magnitude. The angle 

 DC H may be confidered as reprefenting the angle of vifion 

 which the fun fubtends at the horizon. The equal angle 

 H C I, the angle fubtended by the fame body in a more ele- 

 vated fituation, ButDHyHI. Thus the heavenly bodies 

 muft appear enlarged in their vertical diameters, when in the 

 horizon ; and the fame may be (hewn of any other diameter 

 They will therefore appear uniformly enlarged; which was 

 the thing to be explained, 



W. OKELY. 



IV. 



Account of fome Specimens of Bafaltes froin the northern Cnufi 

 of Anlrim. By the Rev. Dr. Will jam Righakdson, 



(Concluded from Page 273.) 



1 HE peninfula of Porlrulh lies about fix miles to the well Remarks on tl 

 of the Giant's Caufeway, and on its eaftern furface alone pre- ^^^^ of Amiin 

 fentsthefe ftrata. 



In the fpace of about 700 yards, it exhibits in miniature thofe 

 changes and interruptions of the ftrata, which occur on the large 

 fcale along the northern bafaltic coalt of Ireland. At the place 

 where it emerges from the ftrand, there firfl occurs a raafscom- 

 pofed of ftrata of the coarfe and filiceous bafalt, placed over 

 each other alternately ; this is fucceeded by an accumulation 

 of regular ftrata of the coarfe bafalt alone. A fecond alterna- 

 tion, and a fecond accumulation of the coarfe-grained ftrata, 

 come in order, and extend to the well called Tubber Wherry, 

 Here commences ^n accumulation of many ftrata of the lih'- 



ceous 



