B. Silliman—Mineralogical Notes. 25 
poles is greater on a part of the armature bey = the two poles 
than it is when poles of opposite signs are o 
n points of the armature between the two (pies the mag- 
netization is greatest when poles of the opposite names are 
oppose north and south pole attract an armature, there- 
fore, with much greater force than two north or two south 
— 
. M. Jamin’s conclusions from the experiments upon an 
ee bar forming a core to the enveloping helices are as follows: 
3°. “If the theory of solenoids is admitted, the action of par- 
allel currents should be to increase the intensity of magnetiza 
tion; on the contrary, it is diminishe 
4°. When the currents in the magnetizing helices run in 
site directions, they should act opposed to each other on 
the currents circulating around the particles of the iron, and 
should diminish each “other's action ; ; on the contrary, it is 
increase 
5°. The action of - oe should be annulled at the mid- 
dle of the bar. It is 
When the bar to “ee ene ek on forms not the core, 
but the armature of two elec peor Ser the effects obtained 
are the reverse of those obtained by M. Jamin, and tend to 
confirm the theory of solenoids. 
Art. IV.—Mineralogical eg Tellurium Ores of Colorado ; 
by B. Stnuiman.* With a note by Arcu. P. MARVINE, on 
the Position and Geology of ‘the Gold Hill Mining Region. 
In May, 1873, I briefly announced the discovery of tellurium 
Se ores at the Red Cloud Mine in Colorado, and stated that 
Prof. N. P. Hill, of Blackhawk, had proposed to send me speci- 
mens of these ores.+ The specimens sent b Prof. Hill were 
long in reaching me, and it is only recently that I have ex- 
amined them. ‘The observations made in the summer of 1873 
by the officers of Dr. Hayden’s Expedition have supplied the 
data needful to understand the mode of occurrence of these ores, 
for the details of which reference is made to Mr. Marvine’s 
notes and map, which form part of this paper. 
" r was communicated at the Apel session (1874) : 
the National Acadomy of Since at Washington. Since then, Mr. Marvine, of 
report, with a brief structure 
pce taal oe I am sees 1 be Cog \asdimara caprogn er Rae sin? detailed 
statement made orally by me to the Academy 
+ This Journal, III, vol. v, 286. 
