ee ag aT ee 
S. L. Penfield—Tiemannite and Metacinnabarite. 451 
The measured angles are the following, the mean of vlosely 
agreeing results being given 
Observed. Calculated. 
70°32! 
On 0,741 A TL. oe 20°81 
ea 7 Os OT 54° 45’ 54°44’ 
Gn &, OO a 118 15° Sate 15°49" 
, OO1 a 15° 50’ 
a» ¢, 001 - 337 31° 10’ 31°13’ 
A number of crystals have the habit shown in fig. 2; only one 
was lustrous enough to admit of measurement. The zone a, 8, 
the most prominent reflections, however, were recorded and 
are given below. The reflection from the faces of a lamplight 
of “schimmer Messung;” the results of which although not 
very exact being sufficiently so to fix the symbols of the differ- 
ent forms. The measurements taken on both sides of, and 
measured from, the cubie face a, are given below. 
: b c € 2) m to) 
Direct reflection 6°11’ 9°17’ 12° 307 ra 
6°17" 9°24? 19°49 17° 17! right. 
opiate te 25’ 9°49’ 12°58’ 17°16" . 
Direct reflection 6° 12’ ti f 
is 6° 7 9°17! 12°20’ 16°267 25°77 31° 23% (left. 
Schimmer B° 60’ 9°" . 11°47" 16° 30" 396° 
Mean 6°10’ 9°32 12°27" 16°47’ 95°38" 31° 297 
Calculated for the following forms. 
16° 13” 9° 277 12° 16 16° 48’ =: 25° 14’ 
(13-1-1, + 13-13), (17-22, tong) (13-22, +5) GU, +5—5),(311, +3—3), 
31° 13” 
(733, +$—$). 
The reflections from w, m and ¢ were very faint, that from ¢ 
being the last trace of reflected light which could be seen on 
turning the crystal. The measurements agree quite well among 
themselves, considering the method used, and warrant my taking 
the above symbols according to which fig. 2 is drawn. The 
form (511, +5-5) shows the greatest variation, but, as it is a 
Prominent form on the simpler and more periect crystals, it 
Seems better to regard the variation as due to error in measure- 
ment than to take the less probable symbol (922, +$—$) with 
calculated value 17° 27’. The only other form m‘(311, —8-3 
Was quite large and very strongly striated parallel to its combi- 
