360 Dana and Brush on the Magnetite i 
fined chiefly to the endosperm, whereas Lenz and myself find 
it nearly all in the chit. On page 258 Dr. Jackson “is able to 
prove that the popping of corn” is due entirely to the decom- 
position of the oil and the formation of carburetted hydrogen . 
as. But it is a matter of el that sweet corn which is 
eds.” It would be ungracious to notice these statements, were 
i not that alias are frequently quoted as a part of our standard 
newenee on this subject. 
Tt will be seen from my analyses that the three first varieties 
of corn which are quite similar in general appearance and in the 
consistency and structure of the kernel, are almost identical in 
composition, while the sweet corn is much poorer in starch and 
richer in sugar and gum as well as in fat. I hope to have an 
opportunity in the future of exten ing my investigations in 
is direction so as to accomplish more perfect separations a and 
ie to examine a large number of varieties ef American maize. 
SS as " 
Sie penbes ia Ty 
Arr. XX XIV.—On the he sonal in the mica of Pennsbury, 
Pa., in reply to Prof. G. Rose ; by James D. Daya and 
Gxores J, Brusu. 
1. Note by J. D, Dana. 
Proressor Ross, of Berlin, in a paper published in the Pro- 
ceedings of the Royal Academy at Berlin pcb erale fiir. 
pies p tah 339), has pronounced the statement in my Min ralogy 
), that the markings in the Pennsbury mica are he to 
hin films of Fo. canbe an error, and has instead called the _ 7 
~The first reference of the species to m 
e b: Prof, Ee and I therefore leave it to 
to mention rie observations upon which the conclusion was 
b They afford full aioe I feel rag tgs that the 
is not hematite, and make it scarcely less certain 
it 
a: 
is 
ments are pion opinions rather than 
facts or demonstrations. a infers from his having seen very 
minute grains of magnetite, even those se iF owpipe 
ductions, which were not sapere that the excessively +] 
transparent crystalline films in the mica are not magneti 
