92 Notice of New Localities of Sahlite, Coccolite, dc. 
sided, and from an inspection of the lamine which are dis- 
tinctly visible, they seem to be single crystals. Iam aware 
that writers on crystallography do not admit the existence 
of reentering angles in single crystals: but I must own my 
Inability to detect any signs of those, which I speak of being 
double. 
There are also some instances of peculiarity in the forms 
of summits, which it may be worth while to notice. I can 
think of no better way to give a just notion of that to which 
I refer than the following. Suppose a person to be form- 
ing a crystal by placing lamine of the proper form upon 
each other, till he had commenced forming the summit by 
lamine of smaller dimensions ; but after the summit was 
partially formed, should determine to carry the crystal 
higher in a form similar to the lower part, and after having 
done so for perhaps half an inch, should then finish with a 
summit. In some cases the appearance is as if this process 
had been repeated the second time before the last summit 
was formed. The partial summits are sometimes like the 
ultimate ones, sometimes unlike. Itis impossible however, 
within the limits of this paper to notice all the interesting 
appearances exhibited on these crystals. Of themselves 
they might form a copious volume for the crystallographer 
to study. 
About four miles from Greenwood in the direction of 
Fort Montgomery, I found a rich locality of the ceylanite, 
or black spinelle’ It was accompanied by brucite, both 
lying in carb. lime. The ceylanite was mostly in octae- 
drons, occasionally truncated, sometimes in hermitrope 
crystals and rhomboids. The crystals were very small, 
rarely larger than a pigeon shot, and most of them much 
smaller, but quite perfect. Some were larger, but imper- 
fect. They were so thick and in such numbers as to form 
large black stripes several inches in breadth, and feet in length, 
inthe limestone. The latter formed ledges of considerable 
extent. I believe that Dr. Mead, of Philadelphia, found the 
ceylanite in a similar connexion last summer at Forest of 
Dean, some miles distant from the locality to which I refer. 
The person who guided me through the wood, brought me 
afterwards from the vicinity of the furnace, some speci- 
mens containing larger crystals; but very defective. I did 
not visit the locality myself. 
