14 



OBSERVATIONS. 



The larger crystals, particularly those from Hungary, are 

 often curved, have frequent transverse rifts, are sometimes 

 broken intirely across, the ends removed to some distance 

 from one another, and the interstices filled up with the sub- 

 stance of which the matrix consists ; sometimes two crystals 

 meet under an angle more or less obtuse, and are joined like 

 the corner of a frame.. The crystals are, moreover, subject 

 to great irregularities, are seldom fully crystallized, and, 

 therefore, rarely acuminated ; the four-sided prisms are often 

 slightly I'homboidal ; the six-sided prisms, from Hungary, are 

 usually dilated, and seem composed of accumulated acicular 

 crystals, from whence arise the columnar distinct concre- 

 tions ; the six-sided prisms, from France, are said to originate 

 from the truncation of two opposite lateral edges of the four- 

 sided prism; the capilliform crystals are sometimes coloured 

 green, from chlorite earth. By some authors, this fossil has 

 been said to resemble red silver ore; but the slightest ac- 

 quaintance with the oryctognostical characters is sufficient 

 to shew the difterence; a geognostical character also fur- 

 nishes us here with an easy means of distinguishing this fossil 

 from other ores of a red colour. Rutile is generally of co- 

 temporaneous foi'mation with its associated fossils; whereas 

 red silver ore, red orpiment, &c. being fonned in veins, are 

 always of later formation than the rock on which they are 



seated. 



