240 NICOLAUS STENO 



wholly rough if the matter has hardened before it has spread 

 sufficiently. 

 p. 41. 2. That the manner in which the crystalline matter is added 

 to the crystal can be distinguished, since where it has hardened 

 suddenly, it reveals a surface full of small elevations like vari- 

 olar postules, as it were, just as small drops of oily fluid are 

 wont to float upon an aqueous fluid ; sometimes it shows also 

 trilateral and depressed pyramids, if it has hardened somewhat 

 more slowly. The tortuous fringes of the descending matter 

 show now the place to which the fluid matter was being added, 

 now the place toward which it was being advanced, now the 

 arrangement of the matter added, that is, which came first, and 

 which last. And in this way certain roughnesses always ap- 

 pear in the crystals of mountains, nor have I ever seen a crystal 

 whose still unbroken surfaces possess the lustre which the rent 

 sides of the same crystal show after it has been broken, how- 

 ever prolix writers on subjects relating to nature become in 

 extolling the lustre of the crystal which is extracted from the 

 mountains. 



,3. That certain intruding solid bodies are enclosed within 

 the crystal itself, as if they had been coated with a sort of glue, 

 in case the crystals did not yet present a hardened surface. 



4. That the crystaUine matter sometimes seems to flow 

 down over neighboring planes. 



5. That when certain small areas on those planes have been 

 left without added crystalline matter, new crystalline matter 

 approaches, and, spreading over the areas, forms cavities there, 

 sometimes producing several layers ; sometimes, again, enclos- 

 ing a part of the external fluid, which in some instances is 

 nothing but air, in others water and air. 



P. 42. The external fluid receives crystalline matter from the sub- 

 stance of the harder stratum, with the result : 



1. That rocks of a different kind, emitting a different fluid, 

 give rise to crystals of a different hue. 



2. That in the same place sometimes the first, sometimes 

 the last, crystals are the darker: but in the same crystal the 

 parts first hardened are sometimes darker than the parts last 

 •hardened. 



