450 Mr. Brooke on crystallized native Oxalate of Lime. 



that as one of the primary planes, and there are other clea- 

 vages parallel to M, and to c of fig. 2. Most of the crystals are 

 twins, and remarkably symmetrical in their form. Fig. 3 is a 

 projection of the terminal planes ; and fig. 4, a projection of the 

 twin crystal in profile, the relation of which to fig. 2, and the 

 other figures, is rendered sufficiently obvious by the corre- 

 sponding letters. All the planes are bright and perfect except 

 M, which is striated by its alternations with u ; and f, which 

 is also striated parallel to the edge betweenyandy. 



Fig. 1. 



Fig. 3. 



The following are the laws and measurements of the planes, 

 for taking the trouble of calculating which I am indebted to 

 the kmdness of my friend Professor Miller of Cambridge. 



Colourless. Transparent to opake. 

 of sulphate of lead. 



Fracture con- 

 Hardness rather less 

 than calcite. Spec. grav. 1-833. 

 Lustre similar to that 

 H. J. B. 



