244 



NICOLAUS STENO 



ANGULAR BODIES OF IRON 



The angular bodies of iron which it has hitherto been my 

 fortune to see ^ reduce to three classes. Of these the first is 

 plane and, being thicker in the middle, gradually grows thinner 

 towards the margins, where it terminates in an edge sharp on 

 every side ; the second is bounded by twelve planes, the third 

 by twenty-four planes. Sometimes an angular body of the 

 second class is bounded by six planes, resembling two trilateral 

 p. 46. pyramids so joined along the bases that the angles of one base 

 bisect the sides of the other. 



The second and third classes of angular bodies of iron agree 

 with crystals in the following particulars : 



1. In the place of production; since the place where iron is 

 formed is partly solid, partly fluid, and is a cavity in the rock. 



2. As regards the place to which matter is added ; since in 

 iron also it is added not to all the planes, but to some only, and 

 not always to the whole of these, nor always at the same time, 

 but now to one, now to another ; now towards the margins, and 

 now towards the middle. 



3. As regards the place from which the iron matter comes, 

 since this matter, also, seems to have flowed forth from the 

 pores of a more solid body. 



4. As regards the manner in which the same matter is di- 

 rected toward the solid by the help of the permeating fluid, and 

 is spread forth and smoothed out upon the plane by the move- 

 ment of the surrounding fluid. 



Iron and crystal differ in matter and form, because the matter 

 of the crystal is translucent, while the matter of iron is opaque. 

 The form of the crystal is bounded by eighteen planes, of which 

 the twelve terminal are brilliant, while the six intermediate are 

 striated. In the second class of iron, however, twelve planes 

 may be counted, of which six are terminal and striated, the 

 other six intermediate and brilliant ; and in the third class of 

 P. 47. iron twenty-four planes may be counted, of which the six ter- 

 minal are striated, and the intermediate eighteen brilliant. Be- 

 tween the terminal striated planes there sometimes lie six other 



* Steno refers to crystals of hematite from the mines on the island of Elba. 



