7 
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ON DIMORPHOUS BODIES. 205 
forces, the intensity of which is inversely as the lengths of these 
axes. Further, that these molecules may unite in the direction 
either of the like or of any of the unlike axes, and that upon the 
junction or approximation of the axes in which they reside the 
opposite polar forces unite and neutralize (?) each other as in 
a chemical compound. 
On these suppositions the influence of circumstances is of a 
less vital character than on that of Sir D. Brewster. They do 
not alter the relative intensity of the forces, they only affect 
the mechanical condition—the relative position it may be—of 
the molecules, so as to allow them to approach and unite in the 
direction of one axis rather than another. 
If the molecules be united in groups three and three, so that 
the unlike axes unite : 
Oss : 
c 
Cc Wate SSB 
ls Shapes CON Ea 
a+b+c.a+h+c.a+h+e 
the resultant axes and the forces resident in them are all equal, 
or the crystal belongs to the regular system. According to 
Voltz all regular forms are built up in this way. 
Again, let them unite in pairs thus, 
Bee NOL Jaa |, oft 
We ey. cat B 
FG 5 Oe . D+ 
and we have a square octohedron, or some other form belonging 
to the pyramidal (2 and 1 axial) system. 
_ If they unite in equal numbers in the direction of each axis 
RRA 258 SO 
BR eM aie ee C 
Date e262 
we have a crystal belonging, like the molecules* themselves, to 
the prismatic (1 and 1 axiai) system. 
_It is easy to see that certain dimensions being given for one 
of these forms, the dimensions of another may be calculated 
from them on the above suppositions. M. Voltz has so far veri- 
fied his principle as to deduce the dimensions of the rhomboid 
of calc spar from those of the right rhombic prism of arragonite, 
and the form of rutile from that of anatase. 
7 7 Itis not necessary that the molecules, to meet the views of M. Voltz, should 
be considered as regular prismatic forms. An oblate ellipsoid has three unequal 
axes, which would answer all the conditions, 
