J. P. Cooke on Danalite from Rockport, Mass. 75 
acid, was determined as eee of — in sis usual way. 
The results of my analyses were as-follow 
: 2. 3 4 Mean 
Silica, - ihe 3154 31°96 31°69 31-73 
Protoxyd = seer A eoes vere 25-71 29°09 27°40 
Oxyd of : 17-90 16°90 19-11 16°14 1751 
Oxyd of manganese, = OS 6-64 617 6°47 6°28 
Glucina, oa f tess 13:86 13-79 13°83 
Sulphur, - : Be veee 5°93 5-02 5°48 
: 102-74 10220 102-23 
Oxygen equivalent to per cent of sulphur; 2:96 2°5 
9978 9969 99-49 
For analysis 4 the material used was a portion of the crystal 
described above. When in mass it had a bright flesh-red ie 
and even in the powder the color was still quite decided. The 
material used in analysis 3 was taken from a wholly different 
ianeapcele aero s 1 and 2 were made before the composition 
of the mineral was correctly seein: and the best method of 
analysis discovered. Hence, only a portion of the bases were 
accurately determined, = only those results are given which 
are known to be trustworthy. The materia] for all the analyses 
was selected —_ reat care; but that used in 4 being a portion 
of a crystal e center of a large mass was unquestionably 
the most pur 
The most ante) theory of the constitution of the mineral, 
to which the above results and the crystalline form both point, 
is that the mineral is an isomorphous mixture of a monometric 
—— with the simple sulphids of iron, zinc, and wags of 
manganese, all of which affect the same crystalline form 
different sulphids must be present in somewhat varying propor- 
tions; for while in 4 the sulphid of iron is evidently in excess, 
the sulphid of zinc equally predominates in 3, and such a differ- 
ence is plainly indicated by the difference of color already men- 
This view is also sustained by the action of different 
acids on the pulverized mineral. Dilute sulphuric acid attacks 
the powder even when cold, sulphid of velngho being evolved, 
while iron and zinc in large quantities, with some glucina, enter 
into solution. Even dilute acetic acid causes an evolution of 
indicus that the gee sulphids are so intimate 
with the silicate that the decomposition of the first aoe 
