ON THE PRIMITIVE FORMS OF CRYSTALS. 73 



place when the obtuse changes into the regular oc- 

 tahedron, all the four axes are in equilibria, or 

 destroy one another. Beyond this inclination the 

 acute octohedrons commence. The four axes com- 

 pose a resultant of an opposite character ; and when 

 the octohedron terminates in the quadrangular 

 prism, the intensity of the resultant becomes 2f. 



The following Table will shew the intensity of 

 the resultant axis in the Octohedron for different 



inclinations : 



Number of the se- Inclination of each separate Intensity and cha* 



parate axes. axis to the resultant axes. racier of the resul- 

 tant axis. 



Four -f axes, 0° 0' 0" 4 -f- axes 



Four + axes, 24 5 42 3 + axes 



Four + axes, 35 15 52 2 + axes 



Four -f axes, 45 0 0 1 -f- axis 



Four -f axes, 54 44 8 0 



Four 4- axes,.,.....,..,.... 65 54 20 1 — axis 



Four 4- axes, , 90 0 0 2 — axes 



The preceding results respecting the rhomboid 

 and the octohedron, are true, mutatis mutandis, of 

 all pyramids, whatever be the number of their sides. 



The general law may be expressed in the follow^ 

 ing manner : 



If any number N of axes of the same character, 

 is placed symmetrically round a given line *, then, 

 when they form an angle of 0° with that line, or coin- 

 cide with it, they will compose a resultant axis in the 



* Two axes can be placed symmetrically only when they 

 are at right angles to one another. 



