HOLWELL CAVERN. 25 
a few very minute ones were visible on the northern or 
shaded side, whereas on being carried down into a dark 
subterranean cellar and deposited on a shelf, prismatic 
erystals of sulphate of strontia rapidly shot out on all sides, 
and at the end of fifty-three weeks exceeded half an inch in 
length- Many years since I filled a tumbler with water 
taken from the pool in Holwell Cavern, and exposed it to 
the action of a small voltaie battery exeited by water alone, 
connecting the opposite poles of the battery with the Hol- 
well water by two platinum wires let fall into the opposite 
sides ofthe tumbler. An electric action immediately took 
place, which continued for nine days, but not finding any 
formation upon either of the wires, I was about to remove 
the whole apparatus, when at that precise moment a party 
of friends called and remained sometime. This most for- 
tunate delay prevented the removal of the apparatus till 
the next or zenth day, when, as I went for the purpose of 
so doing, I plainly observed some sparkling erystals upon 
the negative platinum wire, which proved to be carbonate 
of lime, attracted from the mineral water by the electrie 
action. I afterwards repeated this experiment in a dark 
cellar, and produced a similar result in six days. This 
was the first experiment of the kind. I have at pre- 
sent a glass quart jar, filled with the Holwell water, 
acted on by a small voltaic battery, through the medium 
of two platinum wires. It is placed on a shelf in the 
dark. I have likewise an exactly similar apparatus, alike 
in all respects, except that it is placed on a shelf in the 
light. 'Thhese were both set in action on the 20th of last 
August ; within ten hours crystals of carbonate of lime 
began to form on the negative wire of each, but 
none on the positive, and they have now considerably 
increased on both negative wires; but there isa wide dif- 
1851, PART II. D 
