46 REPORT—1846. 
Notices of Experiments in Thermo-Electricity. By J. Reaper, M.D. 
Some experiments were shown by which a brass bar covered with paper, placed 
in the focus of a reflecting sheet of copper bent into a semicircular form, and at a 
short distance from a spirit-lamp, was made to revolye. This Dr. Reade thought to 
be due to the influence of thermo-electricity. 
On the Electrization of Needles in different Media. 
By Prof. C. Matreucct. 
Professor Matteucci has found that needles electrized in air, in oil, or in water, 
were differently affected by the current, the magnetism varying with the nature of 
the medium in which the needles were placed. The materials employed were the 
oil of turpentine, olive oil, alcohol and water, and also plates of mica. The discharge 
of a Leyden jar was then passed near the needles suspended in these fluids, and the 
amount of magnetization ascertained. 
On Crystallography and a new Goniometer. By H. B. Lerson, M.D. 
This new system of crystallography was, during the last session of the Chemical 
Society, brought under the notice of that body, and illustrated by models and instru- 
ments, Dr. Leeson’s goniometer consists in adapting to a microscope a polarizing 
prism ; the crystal observed through this polarizing eye-piece of course presents two 
faces instead of one, but by turning the eye-piece until these two angles are made to 
correspond, the true angle of inclination from the axial line is obtained, and its value 
is read off from a graduated circle within which the polarizing arrangement moves. 
On the Influence which finely-divided Platina exerts on the Electrodes of a 
Voltameter. By the Rev. T. R. Rozinson, D.D. 
Having occasion some years ago to construct a small voltaic battery on Daniell’s 
principle, and wishing to make it as powerful as was consistent with a limited size, 
I was led to determine its constants by Ohm’s theory. Using the voltameter, and 
grouping observations by the means used in astronomy, I succeeded in this; and 
when Mr. Wheatstone’s paper on the ‘ Rheostat’ appeared, wished to confirm by 
that instrument my results. The facility of its application led me to other examina- 
tions, one of which I have ventured to lay before the Section, as it seems to me im- 
portant in its bearing on a matter lately brought before the scientific world by Grove 
and Faraday, namely the intimate connexion of all or nearly all the molecular forces, 
The galvanometer used by me, being intended to measure powerful currents, con- 
sisted of a simple needle suspended in the centre of a massive rectangle of copper. 
I was in hopes that this simplicity of construction might give some simple relation 
between the deflection and force, but it was not so; the denominator of Ohm’s ex- 
pression of the force of the current is 
R+=r Veo taagd B cos* 6 }. 
as given by careful interpolation; but I have not tried whether this can be deduced 
from theory. The needle’s magnetism was constantly examined and kept at satura- 
tion. The rheostat was of Mr. Wheatstone’s second kind slightly modified, its wire 
copper 7;th of an inch, and 100 turns of it are 70 feet. The value of E, the elec- 
tromotive force of Ohm, or rather the infensity of the sum or difference of the che- 
mical affinities exerted in the cells is, as in Wheatstone’s memoir, expressed by the 
number of turns of the rheostat required to bring the needle from 45° to 40°. The 
determinations of it are very consistent, provided that the magnetism of the needle is 
constané and all the apparatus in given positions *. 
* The author adds the value of E in the following cases :— 
Copper, zinc, dilute sulphuric acid .........seseeeeeeeee peunaaae FEE conssosscsesesecs 2 = oL'U 
Platina, zinc, dilute sulphuric acid ..........sesecscecessnversesreveeors oawd soa sesame ane .. E = 43°0 
Daniell’s cell ....... to seeaccenecerccedcarerstocccgscsnsccsesesrsoncs osegenescecsenadnestane® cote = OF 
Ditto, with mur. acid and ammonio-chloride of COpper .sccsseseceeseceeeeeecsceereceee . E = 539 
Zinc in dilute mur. acid, copper and a mixture of sulph. of copper and nitr.ofammon. E = 68°0 
Groye's)cell, .i3. Wukesssiecscecedéacess sederseseeseecvean edad. Gdssasen tacdbbecncvocccoscabedes Mules Oma 
These values neither change with the concentration of the fluids nor with the temperatures. 
