294 
DR. RITCHIE’S EXPERIMENTAL RESEARCHES 
perimental investigation. This assertion I put to the test of experiment, as 
follows: 
Exp. X. Having cemented a glass tube, about an inch in diameter and four 
inches long, into two wooden boxes A, B, as in fig. 7, and filled the whole 
with water, I placed two plates of copper c, c', having copper wires soldered 
to each, opposite the ends of the glass tube T. The wire proceeding from 
c', after extending about a foot upwards, was bent towards the left at D, and 
then made to descend at E and pass parallel to the needle N S, and thence 
to the end of a battery. The other wire iv was connected with the other end 
of the battery. It is obvious from this arrangement, that the effects of the elec¬ 
tricity arranged in the cylinder of water, and those of the horizontal branch of 
the wire above the needle, would be to turn the needle in opposite directions. 
When the branch G H was further from the needle than the axis of the tube, 
represented by the dotted line, the needle was deflected in obedience to the 
cylinder of water ; but when the wire was brought nearest the needle, it was 
deflected in the opposite direction. 
When the wire was placed at the same distance from the needle as the axis 
of the cylinder, the needle remained perfectly stationary. When a disc of zinc 
was substituted for one of the copper plates, and the wires connected so as to 
form an elementary battery, the needle was deflected with the same force by 
the column of water as by the metallic part of the circuit. Hence it is obvious 
that a cylindrical column of water conducting voltaic electricity deflects the 
needle with the same energy as a metallic wire passing along its axis and 
forming a part of the same circuit. 
22. To complete this part of the inquiry, I was anxious to make a hollow 
column of water revolve about the pole of a magnet. This was accomplished 
as follows : 
Exp. XI. Having procured two thin hollow cylinders of wood, the one about 
two inches and a half in diameter, and the other about an inch and a half, I 
cemented the one within the other at the bottom. Two fiat rings of copper 
were then fixed parallel to each other, at the bottom and top of the cylindrical 
box, the space between them being for the reception of water or diluted acid. 
This annular space was divided into tv/o compartments by thin slips of wood, 
placed perpendicularly to prevent the water revolving without carrying the 
