SUPPLEMENTARY NOTES. 615 
with these there are some which I have not as yet been able to 
refer to any known form of fruit. Coniferous fruits are compara- 
tively scarce, although the remains of Coniferous branches are by 
no means uncommon. A similar discrepancy exists as regards 
the Palms, stems of palmaceous structure being rarely found, 
although the species of fruits of that order are numerous. The 
principal bulk of fossilized woods found in the London Clay 
are decidedly Dicotyledonous, and the great bulk of fossil fruits 
likewise. The internal structure of both fruits and woods is pre- 
served in a most perfect and beautiful manner." 
P. 552. At the meeting of the British Association at Bristol, 
in August, 1836, Mr. R. W. Fox submitted to the Geological 
Section an experiment, showing that the native yellow copper, or 
bi-sulphuret, is convertible into the sulphuret of that metal by 
weak voltaic action. His apparatus consisted of a trough divided 
into two compartments or cells, by the intervention of a mass or 
wall of moistened clay. In one of these cells he put a solution of 
sulphate of copper, and a piece of the yellow bi-sulphuret of 
copper; and in the other cell, some water with a little sulphuric 
acid in it, or water only, without acid, together with a piece of 
Zinc which was connected with the copper pyrites in the other 
cell, by means of a copper wire. 
This simple voltaic arrangement quickly changed the surface 
of the copper ore from a yellow to a beautiful iridescent colour, 
afterwards to purple copper, and finally, in the course of a few 
days, to the sulphuret, on which metallic copper was copiously 
deposited in brilliant crystals. When this process was continued 
for some weeks, and sulphate of copper added from time to time, 
the sulphuret of copper formed rather a thick crust immediately 
under the metallic crystals, and appeared almost black and some- 
what friable. He considered that the oxide of copper in the so- 
lution parted with its oxygen to a portion of the sulphur of the 
bi-sulphuret, thus forming sulphuric acid, which was transmitted 
through the clay to the Zinc in the other cell, whilst the de-oxydized 
copper was deposited on the electro-negative copper ore. These 
results seemed to explain the reason why metallic copper is found 
in the mines in contact with the sulphuret and black copper ore, 
and not with the yellow bi-sulphuret of that metal ; and likewise 
