TRANSACTIONS OF SECTION B. 983 
The current was small owing to the great internal resistance of the cell, and 
attempts were made to reduce this resistance by diminishing the proportion of free 
sulphur. But it was found that when the resistance was reduced in this manner 
the E.M.F. was also reduced, and when there was nothing but simple copper 
sulphide between the plates, there was no sensible E.M.F. whatever. 
Another cell was made in which powdered silver sulphide without any free 
sulphur was compressed between plates of silver and copper. This arrangement 
generated a current, the direction of which was opposite to that produced by the 
cells above described, but the E.M.F. rapidly fell off, and in three or four days had 
almost completely disappeared. 
When a similar cell was constructed in which the silver sulphide was mixed 
with sublimed sulphur and placed in the form of a powder between the plates, the 
direction of the current was, as with simple silver sulphide, from copper to silver. 
But if the mixture was first fused and the plates between which it was com- 
pressed heated, the current generated by the cell when cold was in the reverse 
direction. Sulphide of copper was undoubtedly formed in the process of con- 
struction. 
Consideration of these results led the author to believe that the sole function of 
the free sulphur in the copper sulphide cell was to form a film of silver sulphide by 
direct combination with the silver plate. A cell was therefore made as follows :— 
A layer of copper sulphide was spread upon a plate of copper, a polished steel 
plate was laid upon the sulphide, and the whole was strongly compressed in a vice. 
The steel plate was then removed and a thin layer of silver sulphide was spread 
upon the smooth surface of the copper sulphide. The cell was completed by 
pressing a silver plate upon the silver sulphide. This was found upon trial to give 
a current which, with an external circuit of low resistance, was many times 
stronger than that generated by any of the cells previously made. Its action was 
probably analogous to that of a Daniell’s cell consisting of plates of zinc and 
copper in solutions of zinc sulphate and copper sulphate. The quantity of the 
copper sulphide would be gradually diminished, copper being deposited on the 
copper plate, while the quantity of the silver sulphide would continually increase 
with consumption of the silver. 
A very curious experiment observed in the course of the experiments was the 
following :—If a battery current was passed for a short time through a cell con- 
taining two silver electrodes embedded in a mixture of sulphur and copper sulphide, 
the cell after being disconnected from the battery generated a current of very short 
duration (not impossibly due to thermo-electric action) in the direction opposite to 
that of the battery current; and this current, which rarely lasted for more than 
two or three minutes, was followed by another which was in the same direction as 
the battery current, and was generally maintained for several hours. 
7. A Theory of the Connection between the Crystal Form and the Atom 
Composition of Chemical Compounds.’ By WiLL1aM Bar1ow. 
The author bases a theory of the origin of the symmetry of crystals upon the 
hypothesis that the different kinds of chemical atoms of a crystallising body so 
far preserve their individuality in the combined state as to personally attract or 
repel one another differently. 
His theory is that liquid matter in the act of crystallising, just before solidification 
takes place, has the chemical atoms of different kinds which compose it sym- 
metrically arranged in space with respect to one another, and that this symmetrical 
disposition of the atoms is the direct consequence of different degrees of attraction 
and repulsion exercised by the different kinds of atoms during fluctuations in. the 
distances between them which are caused by waves of alternate condensation and 
rarefaction traversing the mass. He supposes that crystallisation occurs only in 
those cases in which the different kinds of atoms are present in such proportions as 
will admit of the necessary symmetrical arrangement. 
1 Published in eatenso in the Chemical News, January 1 and 8, 1886. 
