272 Scientific Intelligence. 
towards which the condition always tends, but from which it may 
diverge considerable from external causes, without destroying alto 
gether the equilibrium. 
The subject of composition by complete interpenetration and the sol- 
dering of crystals occupies much of M. D izeaux’s memoir. The 
crystals are united irregularly, almost as if melted into one another, 
the union being in an exceedingly complex manner. These forms 
were well illustrated by Mr. Gustav Rose. M. Descloizeaux has 
examined them by secti in various directions, and studied both 
their crystalline appearances and their optical characters, finding 
m e 
The various appearauces are shown in the engravings. The ef- 
same structure, and almost always show a more or less complicated 
arrangement of plates of contrary rotation. 
The planes of composition are usually parallel to the faces of the 
pyramid, more rarely to the rhombic faces of Haiiy ; sometimes paral- 
ron. The arrangement of quartz of inverse rotation in layers parallel 
to certain faces of the crystal seems at first 10 accord with the law o 
a 
isters the facts. The plates are numerous and of the highest 
bitereste->L’ Institut, No. 1117. ; oe 
8. Note gn Heulandite and Scapolite from Arendal, by E. Zscuav. 
—From the chemical composition of the varieties of these minerals 
which occur at Arendal may be noticed an interesting analogy. The 
following analyses (1, 11) of Scapolite are by von Rath, and (11) of 
Heulandite by Sjogren. 
i ai. 
Si 45°05 46-82 Si 58-41 
Al 25:31 2612 Al (16°56 
Fe 202 1:39 : Ca 789 
Ca 1730 17-23 Mg Mn & alkalies 054 
Mg 0°30 °.:26 H 1653 
55 (097 
Na 645 6°88 . 
H 1:24 033 
sae iaraca? Sphere = i anaemia. eas i 
(Ca, Na) Si2z24 Si. Oa Si+41 Sit+eH. 
