Organic and Inorganic Forms. 85 



itself, and in the condition of the matter, there is a 

 double reason for thinking that roundness is no peculiar 

 characteristic of organic form. 



Again : instead of being solid and homogeneous 

 crystals frequently resemble cells in the possession of 

 internal chambers. Cavities are well known to exist in 

 many saline crystals. Cavities, which frequently contain 

 minute detached grains, are very common in the 

 spherules of oolite and pea-stone. In silex, again, the 

 condition is similar : and the well-known flint nodules 

 are hollow egg-like stones, containing a smaller nodule, 

 which is often so loose as to rattle when shaken. The 

 wall of these earthy chambers, moreover, is occasion- 

 ally composed of layers so arranged as to be not unlike 

 the laminated coats of the true cell. In the granules 

 of oolite and pisolite, for example, this arrangement is 

 very perfect, and a polished cross-section agrees closely 

 with that of the spine of a sea-urchin. The laminated 

 structure, also, is seen where no cavity exists, as in the 

 globular masses of resinous trachyte, or pitch-stone 

 porphyry, met with in one of the small islands near 

 Terracina or Gaieta, which when acted upon by the 

 weather separate readily into concentric scales like 

 those of a bulbous root. 



Other and higher shapes, which seem to reflect the 

 images of polypes and flowers and branches, are also to 

 be found in the domain of the crystal. The flakes of 

 snow and hoar-frost, for example, are composed of 

 crystals arranged in such a manner as to afford no inapt 

 likeness to the disc of the flower or polype. In stalac- 

 tite pendants are often found the images of fungoid 

 plants : and in the mammoth-cave of Kentucky Dana 

 describes alabaster rosettes a foot in diameter, sur- 

 rounded with circlets of elegant leaves, and vines with a 



