38 Brush and Dana—Fairfield County Minerals. 
Calculated. Measured. 
bas 010,121 = 49° 2)’ 
Inp 110,111 = 49° 69” 49° 55’ 
gas 120,121 = 39°13’ 
pap 111,111 = ¥*46° 28” 46° 28” 
qag’ 232.232 = 65° 33’ 
roe @ 121,121 = 81°18’ 
pp Wid = et SF ¢i° 2 
q.q" 232.232 — 55° 22’ 
$3” 121,121 = 49° 34’ 49° 397 
pap” lll,Ti1 = 80° 2” 80° 0” 
qay”’ 232,232 = 91° Vl’ 
exe” 121.121 ° = 101° 33” 
as 111,121 = 17° 267 at° 18/ 
Eosphorite. Childrenite. Childrenite. Childrenite. 
Tavistock (Cooke.) Hebron (Cooke.) Tavistock (Miller.) 
75° 247 74° 20’ 75° 467 
ik AR" 41 
sas’ 81° 18” 81° 20 80° 38 82° 8” 
sae 49" 34" ao 50° 36” 49° 56” 
ene” FOL" $3’ 101° 43” 101° 367 102° 41’ 
In order to bring the crystals of childrenite into this posi- 
tion the clinodome (2-3, or n of Miller) is made the unit prism. 
Optical erties.—A careful examination in the stauroscope 
proved that the three axes of elasticity coincide with the crys- 
talline axes, showing that the crystals are really orthorhombic. 
The optic axes lie in the macrodiagonal section, or plane of 
cleavage, the acute bisectrix (first mean-line) being normal to 
the Need en and the obtuse bisectrix consequently to 
ane. The axial angle could not be obtained with 
very great accuracy, owing to the fact that the best sections 
left much to be desired in the way of clearness. The measure- 
ments gave :— 
2E = 54° 30’ _ red rays. 
= 60° 30 blue rays. 
The dispersion of the axes is strong, v>p; the character of 
the double-refraction is negative. 
* This Journ., II, xxxvi, 257, 258. 
