Measurement and Cleavage of certain Primitive Crystals. 263 



On submitting to the reflecting goniometer several crystals cleaved 

 parallel with the planes P' P', they all afforded the result of 76° 18', 

 coinciding therein with several fragments in the form of the primi- 

 tive crystal fig. 13, which also gave 103° 42' as the value of the 

 obtuse angle. I am therefore induced to conclude that the primitive 

 crystal of the sulphate of lead is a right prism with rhombic ter- 

 minations, whose angles are 76° 18' and 103° 42'. 



2l 2 



