1824.] Col. Beaufoy's Astronomical Observations. 121 



remarkable that they should each constitute separate minerals 

 in connexion with very nearly equal proportions of the same 

 earths — and as it occurred to me as being within the verge of 

 probability that these two alkalies might, by coalescing and 

 uniting themselves to the same or other earths, form another 

 compound body which would probably in that case have for its 

 primary form, one in which the planes would meet at angles 

 different to those either of felspar or cleavelandite, I have been 

 anxious to detect any such difference if it exists, but without 

 success ; for in every instance the angle obtained belonged to 

 the primary form either of the one or the other of the above- 

 mentioned mineral. 



It may be added that although these minerals are sometimes 

 sufficiently distinct in the same specimen, there is no one cha- 

 racter belonging to either which adequately distinguishes it from 

 the other at first sight ; the most important feature is, that in 

 general the cleavage planes of felspar are more brilliant than 

 those of cleavelandite ; and hence it will be difficult hereafter to 

 describe a rock in which one of these minerals appears to be an 

 ingredient, without first having recourse either to the chemist or 

 the goniometer, in order to prove that it is not the other. 



Article XI. 



Astronomical Observations, 1823. 

 By Col. Beaufoy, FRS. 



Basket/ Heath, near Stanmore. 



Latitude 51° 37' 44'3" North. Longitude West in time 1' 20*93". 



Dec. 30. Emersion of Jupiter's second J llh 33' 34" Mean Time at Bushey. 



satellite ( 11 34 55 Mean Time at Greenwich. 



Jan. 6. Emersion of Jupiter's first ^ 9 12 47 Mean Time at Bushey. 



satellite < 9 14 08 Mean Time at Greenwich. 



Jan. 1 1 . Emersion of Jupiter's first j 16 38 37 Mean Time at Bushey. 



satellite ( 16 39 58 Mean Time at Greenwich. 



Jan. 12. Occultation of a small star by < $ 5 



the moon. Immersion ( 



Jan. 12. Emersion of Jupiter's third J 8 24 20 Mean Time at Bushey. 



satellite } 8 25 41 Mean Time at Greenwich. 



Jan. 13. Emersion of Jupiter's first? 11 08 14 Mean Time at Bushey. 



satellite ( 11 09 34 Mean Time at Greenwich. 



N. B. Jupiter's Limb was tremulous and ill defined. 



