Generation of Electrical Currents. 85 
however, failed to prove what was sought. Since then I have 
found that, by regulating the section of the joint the galvanic 
current has to cross, it can be readily shewn that the current in 
the outer arms increases and diminishes, and this with arms of 
the same metal, where heat gives very little thermo-electrical 
action. Leta cross be made of two strips of rolled zine, cut 
off the same sheet of metal, when the section of the central 
joint is quite small ; a large portion of the current appears in 
the outer arms of the cross; but as the section of the joint is 
enlarged, the quantity of electricity which appears in the 
outer arms decreases, until with a large section it disappears 
altogether. 
The annexed dia- A 
gram represents a 
cross, composed of 
three bars of bis- 
muth; AC, a long 
bar; and DE and 
FB two half bars. 
The ends E and F 
of the half bars wereD 
placed in metallic 
contact with the bar 
AC, but with a space 
intervening between 
them at G, whereby 
a galvanic current, 
passing along DB, 
had two joints to 
cross, one at E and 
another at F. When 
the space at G was HI 
closed, by pressing the points of the bars together into metal- 
lic contact, then a galvanic current passing along DB had 
only one joint to cross. The extremities of the bars at A 
and D were connected by wires with a Smee’s battery of one 
or more number of plates; and the other extremities at B 
_and C had wires BI and CH soldered to them. 
_ The wires at H and I were connected with a galvanometer. 
