218 £. S. Dana—Garnets from the Trap Rocks of New Haven. 
Garnets from Mill Rock. 
The other garnet locality is at the west end of Mill Rock. 
In appearance and in method of occurrence the garnets here 
found are a decided contrast to those that have been just de- 
seribed. They occur on the line of contact between the trap 
and the adjoining sandstone, and probably owe their origin to 
the metamorphic action of the heat of the erupted rock. They 
are found best in seams and little cavities in the trap, where 
other forms occurring with this are: 
2-2, 3-3, and H. The adjoiming 
figure shows the habit of the crystals. 
The following angles were measured 
to determine these forms. 
For $-3A3-3 (over H) =136° 15’, required 135° 59’ 48”. 
“« «adjacent (edge B)=149°16’, required 149° 16’ 38”. 
For 64-4 edge B =178° 15’, required 178° 5’ 
“ce “cs 4 8 —178° 56’, “cc 179° 6 
. 
' 
. 
Of the above enumerated forms, the basal plane (/) is quite 
rare with this species, the tetragonal tris-octahedron 3-3 is new, 
though it has been observed on fluorite, and also by Klein (as 
a hemihedral form) on sphalerite; and the hexoctahedron 
admit of any chemical examination, but in view of their siml- 
larity of form and color, they may safely be referred to the 
to obtain enoug 
character remains undetermined. 
