On Sir G. C. Haughton’s Experiments in Electricity. 265 
In conclusion I may observe, that tin is the only simple sub- 
stance yet known, the crystals of which belong to the pyra- 
midal system, and the only crystallizable metal not belonging 
either to the octahedral or rhombohedral system. It is also 
I believe the first instance in which the action of voltaic elec- 
tricity has led to an accurate knowledge of a new crystalline 
species. 
Cambridge, Feb. 3, 1843. W. H. Mirzer. 
P.S. Since the above was sent for insertion in the Philo- 
sophical Magazine, I met with the following passage in a 
memoir by Professor Frankenheim, entitled ‘ System der 
Krystalle,” forming part of vol. xix. of the Nova Acta Acad. 
Nat. Cur. “ According to Breithaupt, tin occurs in hexa- 
gonal prisms in the tin furnaces of Cornwall. By reduction 
at a low temperature I have always obtained it in tesseral 
forms.” The hexagonal prisms of Breithaupt are in all pro- 
bability an alloy of tin and copper Cu Sn, crystals of which 
from a specimen in the Mineralogical Museum of Strasburg, 
were described by me in the Philosophical Magazine for Fe- 
bruary 1835. It does not appear whether Frankenheim ob- 
served any forms of the octahedral system excepting three 
faces at right angles to each other. The occurrence however 
of three faces at right angles to each other, though not an ab- 
solute proof that the crystals belong to the octahedral and not 
to the pyramidal system, would afford a strong presumption 
that they did in the present instance, inasmuch as I have never 
been able to detect the slightest indication of a face perpen- 
dicular to the axis of the pyramid. 
Cambridge, March 8, 1843. W.H.M. 
XLVI. On Sir G. C. Haughton’s Experiments in Electri- 
city related in the last Number. By J.P. Joure, Esq. 
To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, 
AtLLow me to occupy a small portion of your space with 
a few observations on the subject of an interesting com-~ 
munication by Sir G.C, Haughton, inserted in your last 
Number. 
On repeating the experiments on the action of frictional 
electricity upon the galvanometer, I find that the pheenomenon 
to which Sir Graves has called attention is simply an example 
of the repulsion of bodies which are in the same electrical 
state, and is not sensibly owing to the minute currents which 
