1874.] Physics. 279 
Mr. J. A. Fleming, B.Sc., read a paper on the “Contact Theory of the 
Battery.” After discussing the most recent views regarding the conta& and 
chemical theories, Mr. Fleming exhibited the action of his new battery, in 
which metallic contact of dissimilar metals is completely avoided. The 
battery consisted of thirty test-tubes of dilute nitric acid alternating with the 
same number of tubes of pentasulphide of sodium, all well insulated. Bent 
strips of alternate lead and copper connected the neighbouring tubes. By this 
device the terminal poles are of the same metal. On connecting with a 
coarse galvanometer, the needle was violently and permanently deflected. 
Tested by the quadrant electrometer, the potential was shown to increase 
regularly with the number of cells. The sixty cells on first immersion showed 
a potential exceeding that of 14 Daniell’s cells. The principle upon which 
the action depends is that, in the acid, lead is positive to copper; in the sul- 
phide it is negative. Mr. Fleming further showed how, by using the single 
liquid, nitric acid, and the single metal, iron, a single battery could be con- 
structed, provided one-half of each iron strip were rendered passive. In 
this form, also, no metallic conta& occurred. 
Prof. F. Guthrie exhibited experiments illustrating the distribution of a 
galvanic current on entering and leaving a conducting medium. This was 
shown in the case of solids by the stratification of iron-filings on sheets of 
copper and lead. The effect of the distribution on a'magnetic needle which 
is hung near a condu@ting vertical sheet in the magnetic meridian—into the 
upper horizontal edge of which a current enters, and out of which it passes 
at the same elevation—is to alter the direction of the needle’s direction of 
turning, according as the needle is lowered or raised. At a distance from the 
upper edge of one-third the distance of the interval between the poles, the 
needle is at rest. A similar effect was shown in a liquid conductor. 
The following are the officers of the Society for the first Session :—President, 
J. H. Gladstone, Ph.D., F.R.S. Vice-Presidents, Prof W. G. Adams, F.R.S.; 
Prof. G. C. Foster, F.R.S. Secretaries, Prof. E. Atkinson, Ph.D., York Town, 
Surrey; Prof. A. W. Reinold, M.A., Royal Naval College, Greenwich. 
Treasurer, Prof. E. Atkinson, Ph.D. Demonstrator, Prof. Frederick Guthrie. 
Other Members of the Council, W. Crookes, F.R.S.; Prof. A. Dupré; Prof. 
T. M. Goodeve, M.A.; Prof. O. Henrici; B. Loewy; E. J. Mills, D.Sc. ; 
H. Sprengel, Ph.D. 
Dr. Geissler, of Bonn, Germany, whose name is inseparably associated 
with some of the most beautiful experiments that can be performed 
by the agency of electricity, makes an electrical vacuum tube that may be 
lighted without either induction coil or frictional machine. It consists of a 
tube an inch or so in diameter, filled with air as dry as can be obtained, and 
hermeticaliy sealed after the introduction of a smaller exhausted tube. If 
this outward tube be rubbed with a piece of flannel, or any of the furs gene- 
rally used in exciting the electrophorus, the inner tube will be illumined with 
flashes of mellow light. The light is faint at first, but gradually becomes 
brighter and softer. It is momentary in duration; but if the tube be rapidly 
frictioned, an optical delusion will render it continuous. If the operator have 
at his disposal a piece of vulcanite, previously excited, he may, after educing 
signs of electrical excitement within the tube, entirely dispense with the use 
of his flannel or fur. This will be found to minister very much to his personal 
€ase and comfort. He may continue the experiments, and with enhanced 
effect, by moving the sheet of vulcanite rapidly up and downat a slight distance 
from the tube. This beautiful phenomenon is an effec of indudtion. 
In a note on a remarkable production of light in grinding of hard stones, 
Dr. Noéggerath refers to a visit made to some agate works at Oberstein 
and Idar, in which various kinds of hard stone are pressed by the 
workmen (with their hands) against quickly-revolving grindstones. The 
transparent stones become pervaded throughout with a yellowish-red light, 
like that of red-hot iron. Opaque stones give a red light at the place of con- 
tact, with halo and sparks. Dr. Noggerath thinks the phenomena worth 
