(4S) 
^i;t of Iron is chansed into the Third 
ibrt. 
But now, that after this manner out 
of a Body of Twelve planes is made a Bo¬ 
dy of Twenty four planes, I Gonclude 
from hence: i. That in the fame Aggre- 
gat of Irombodies, almoft all the thin¬ 
ner ones have only twelve planes, but the 
thicker ones, twenty four. 2. That in 
fome Bodies of Twelve planes there ap¬ 
pear the Beginnings of Triangular planes, 
which are acceifory, and being continued 
make up a Body of Twenty four planes. 
In theTriangular planes 1 have often 
bbfcrved fo perfed a frnpothnefs, that 
there appear’d not the leaft unevennefs 
to the eye 5 which I never yet faw in any 
Chryftal.* In others, I have feen lelfer 
Circular planes put upon greater, the 
fuperiour of which were. For the moft 
partjclole tp the vertex of the Triangles 
lb that it may be doubted, whether the 
Five«iided planes be not made up of the 
bafes oi the Triangular planes, confider- 
ing thatfootfteps of ftreaks are there ex¬ 
tant parallel to them. 
