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 primitive 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 terminations, whose angles are 76° 18′ and 108° 42′.
