1823.] CoL Beaufoy's Astronomical Observations, 43 



Fig. 1 represents the prism with the mo- 

 difying planes which I have observed on two 

 or three crystals, and on these only, out of a 

 considerable number that I have examined. 



Their general form is that shown in fig. 2, 

 in which two of the planes a alternately 

 efface all the other terminal planes at the 

 two extremities of the prism. There are 

 also many crystals which nearly resemble 

 fig. 2, but in which the planes a and a'' are 

 visible, although very minute. This irregu- 

 larity of form is of the same character as has ^^S- ^* 

 been already noticed as belonging to sul- 

 phate of magnesia. The measured angles 

 are as follows : 



M on M' 90° 00' 



c on M 

 c'onM 

 fl onM 

 a' on M, or M 



.-} 



132 45 



'} 



112 

 114 



40 

 00 



Article X. 



Astronomical Obsei-vationsy 1823. 

 By Col. Beaufoy, FRS. 



Bushel/ Heath, near Stanmore. 

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



Maj 18. Emersionof b^ Leonis from the moon . I3h 41' 18" Siderial Time. 



