146 
parallel to the alternate edges” of the hexagon. In a num- 
ber of large crystals from Ticonderoga, however, he had 
found, as their especial peculiarity, two triple sets of stria, 
one like that referred to, and the other precisely the reverse, 
crossing the crystal at right angles to each pair of opposite 
edges, and inclined 80° to the two intervening pairs. In 
either case, the intersections of the striz of each set with one 
another, form angles of 60°, covering the crystal with figures 
of rhombs and equilateral triangles, which are often sharply 
reproduced on the smooth surfaces of the felspar matrix. 
These two sets of striz never occur together on the same 
surface, but appear to alternate throughout the crystal, on 
opposite sides of its cleavage laminze ; though this alternation 
does not seem always regular. 
Prof. Martin described and drew these striations particu- 
larly, regarding them as showing that the crystal of graphite 
is really an orthorhombic prism of 60° and 120°, twinned by 
threes into an apparent hexagon, on the same principles as 
those developed by Prof. J. P. Cooke in his recent paper on 
the Vermiculites. 
In such case, the strize mentioned by Prof. Dana are 
probably brachydiagonal, while those that he had now dis- 
covered would be macrodiagonal. The two series might 
alternate on the opposite sides of each lamina; or they 
might all be macrodiagonal, if the macro-axes of all the 
rhombie, or elliptical, molecules in a given lamina were al- 
ternate with those in the adjacent lamina. The obscurely 
hexagonal, and sometimes accurately circular, outline of 
many of the crystals would favor the latter view. In some 
cases, however, the crystals present strongly rhombic forms, 
in one instance with well-marked reéntering angles. 
[The whole paper was so largely dependent upon illustra- 
tions, and upon citations from the views of Prof. Cooke, as to 
be difficult of reproduction in an abstract. It will probably 
appear further in the Annals, Vol. XI]. 
Pror. Eanuesron and Pror. Lerps expressed much inter- 
est, and hoped that the subject would be carried on to a still 
fuller investigation, as the discovery would be highly impor- 
tant in mineralogy, should it be positively established. 
Pror. E@LEston followed with a paper “‘ On the Striations 
of Crystals.” He dwelt at some length upon the nature and 
causes of this phenomenon, of which little is generally known. 
