118 PHYSIOGRAPHY. CLASS H. 



Compound Varieties. Twin crystals : axis of 

 revolution perpendicular, face of composition paral- 

 lel to a face of P -f- oo. The individuals generally 

 continued beyond the face of composition. This 

 composition is very similar to some that occur in 

 prismatic Lime-haloide. The product of it is a six- 

 sided prism, having four edges of 117 19' and two 

 of 128 22'. As in the above mentioned species, 

 particles of the two individuals alternate in parallel 

 layers with each other. Indistinct globular masses : 

 surface drusy, composition columnar. Massive : 

 composition columnar, the individuals generally 

 straight, long, and a little divergent ; the compo- 

 sition is seldom granular. 



OBSERVATIONS. 



1. KLAPROTH found a variety of the present species to 

 consist of 



Strontia 69-50. 



Carbonic Acid 30-00. 



Water 0-50. 



It is Sr C 2 , which corresponds to 70-16 of Strontia, and 

 29-84 Carbonic acid. It is soluble with effervescence in 

 the muriatic and nitric acids ; and paper, dipped into this 

 solution and afterwards dried, will burn with a red flame. 

 It melts before the blowpipe at a temperature not very 

 elevated, but only on the thinnest edges. It intumesces, 

 and spreads a brilliant light ; the flame at the same time 

 assumes a reddish hue. It is dissolved by borax with a 

 violent effervescence into a clear globule, 



2. The repositories of this species of Hal-baryte are me- 

 tallic veins traversing primitive and transition mountains 

 either containing hexahedral Lead-glance, prismatic Hal- 

 baryte, &c. or prismatic Arsenical-pyrites, rhombohedral 

 Quartz, and other species. It seems also to occur in beds. 



