182 G. W. Hough on the Galvanic Battery. 
are unnecessary. I hope before long to be able to obtain a 
sufficient quantity of the mineral to continue the study of its 
composition. The results here given are sufficient to demon- 
strate it to be a new species, and I believe it to be the only 
observed native fluo-arsenate. I propose for it the name Du- 
rangite, 
Preliminary Note on the Crystallization of Durangite; by 
JoHN M, Buake. 
I defer, for the present, a detailed account of my observations 
on this mineral, with the hope that I may have an opportunity 
to examine other specimens better adapted for measurement, 
and the study of the habit of the species. The angular meas- 
urements, as well as the optical characters distinguish the spe- 
cies, and show that the crystals are monoclinic, and that they 
do not correspond either with amblygonite or the other anhy- 
drous phosphates and arsenates, of which I have been able to 
find crystallographic descriptions, and belonging in the division 
to which the chemical characters appear to assign this mineral. 
An approximation in all the angles, to those of keilhauite, 
and sphene, is interesting. The figure of keilhauite* is so goo 
a representation of the crystals of Durangite, that for present 
purposes it may be used for illustration, by making J the cleav- 
age plane, and omitting O and the plane there marked —21, 
which were not found, and adding 47, which occurs in sphene, 
and on Durangite is a small plane of infrequent occurrence. 
Art. XX.—Remarks on the Galvanic Battery; by G. W. 
Hoveu, Director Dudley Observatory. 
THE constant use of Daniell’s battery for nearly ten years, 
ade us desirous of more fully understanding the mode of its 
action, and the cause of the decline in the strength of the elec- 
tric current. For this purpose, during the past year, a series 
of experiments were instituted, with batteries of various forms. 
As they were undertaken solely for the purpose of securing the 
best form of battery for every day use, delicate instruments 
were not provided, and consequently great precision of measure- 
ment could not be obtained. 
_ The Galvanometer consisted of a steel needle one and a half 
inches in length, attached to a light strip of brass, having ® 
radius of five inches, This needle was mounted horizontally 
over a coil of silk-covered copper wire. The graduation of 
* See Dana’s Mineralogy, 5th edition, p. 387. 
-t Abstract read at the Chicago meeting of the American Association. 
* 
