in the Mica of Pennsbury, Pa, 361 
He infers, from his having observed scales and markings of he- 
matite in some micas, that those of the mica in question are 
probably hematite. Finkener having, at Professor Rose’s re- 
quest, examined the Pennsbury mineral and found in it pro- 
toxyd of iron, he infers that this protoxyd is an accidental in- 
gredient, as is true in the case of some hematites, and not evi- 
dence that the species is magnetite. Rammelsberg thinking 
he has reason to believe that the oxyd of iron coloring green 
bottle glass is magnetite, the inference is drawn that magnetite 
if transparent would be green, and hence the mineral by its 
brownish shades shows that it is not magnetite, Such evi- 
dence has not great scientific value. 
The seemingly decisive fact brought forward, to which the 
above inferences are added, relates to the color of the mineral. 
In my Mineralogy the films are said to vary from “colorless to 
pale smoky brown and black.” Professor Rose states that, be- 
sides having these colors, it is also sometimes red and yellow. 
his was, from the first, observed to be true by Professor 
Brush and myself. But it was further seen by us that the red 
and yellow colors were always a result of alteration ; and we 
are sure that if Professor Rose had examined the hundreds of 
specimens that have been at our disposal, he would not have 
failed to detect this. He argues from the occasional red color 
which he observed that the mineral is not magnetite, but he- 
matite; when in fact the range of colors from colorless to 
black proves just the reverse, or at least that the species is not 
hematite, 
In applying the term dendrite to these markings I had refer- 
ence to the dendritic forms they generally present, .and not to 
the time or mode of origin, on which latter point I held the 
Same view with that sustained by Professor Rose. 
2. Note by G. J. Brush. 
ciently thick ; that this color shaded into dark brown ; and this 
gradually into a delicate smoky hue, still retaining the 
i ess. 
changed to a bright red or yellow color. A large number of 
Specimens, however, showed no evidence of alteration. 
