430 



SCIENTIFIC RECREATIONS. 



or shorter than the former two. In this system crystallize sulphate of nickel, 

 zircon, oxide of tin, etc. 



The fourth, or RHOMBIC system, or the trimetric. Here we have three 



Fig. 447. Oxide of tin. 

 Fig. 446. Galena, or sulphide of lead. 



rectangular axes, all unequal and intersecting at right angles. The sulphate 

 and nitrate of potassium crystallize in this system. 



The fifth is the oblique, or MONOCLINIC system, which displays three 



Fig. 448. Rock crystal 

 second system. 



Figs. 449 and 450. Quadratic, or third system. 



Fig. 451. Prism of qua 

 dratic system. 



unequal axes, two of which are at right angles ; the third, or principal axis, 

 is at right angles to one and oblique to the other of the preceding. Ferrous 

 sulphate, tartaric acid, and gypsum crystallize in this system. 



Fig. 453. Crystals of the fifth system. 



The sixth) or TRICLINIC system, or the doubly oblique. In this system 



i. 452. Rhombir, or 

 fifth system of crystals. 



