544 PROF. HENRY ON THE INFLUENCE OF A SPIRAL CONDUCTOR 
arrangements. If the battery formerly described* be arranged as a ca- 
lorimotor, and one end of a large spiral conductor be attached to one 
pole, and the other end drawn along the edge of the connector, a series 
of loud and rapid explosions is produced, accompanied by a brilliant de- 
flagration of the metal; .and this takes place when the excitement of the 
battery is too feeble to heat to redness a small platina wire. 
1¥. A number of experiments were made to determine the effect of 
introducing a cylinder of soft iron into the axis of the flat spiral, in 
reference to the shock, the spark, &c.; but no difference could be ob- 
served with the large spiral conductor; the effect of the iron was 
merged in that of the spiral. When, however, one of the smaller rib- 
bons was formed into a hollow cylindrical helix of about nine inches 
long, and a cylinder of soft iron an inch and a half in diameter was 
inserted, the spark appeared a little more intense than without the iron. 
The obliquity of the spires in this case was unfavourable to their mutual 
action, while the magnetism was greater than with the flat spiral, since 
the conductor closely surrounded the whole length of the cylinder. 
I would infer, from these experiments. that some effects heretofore 
attributed to magneto-electric action are chiefly due to the reaction on 
each other of the several spires of the coil which surround the magnet. 
13. One of the most singular results in this investigation was first 
obtained in operating with a large galvanic battery. The whole in- 
strument was arranged as a calorimotor of eight pairs, and a large 
spiral conductor introduced into the circuit, while a piece of thick 
copper wire about five inches long united the poles. In this state 
an explosion or loud snap was produced, not only when the contact 
was broken at the spiral, but also when one end of the short wire 
at the other extremity of the apparatus was drawn from its cup. 
All the other short moveable connectors of the battery gave a similar 
result. When the spiral was removed from the circuit and a short wire 
substituted, no effect of the kind was produced. From this experiment 
it appears that the influence of the spiral is exerted through at least 
eight alternations of zine, acid, and copper, and thus gives to a short 
wire at the other extremity of the circuit the power of producing a 
spark. 
14. The influence of the coil was likewise manifest when the zine 
and copper plates of a single pair were separated from each other to 
the distance of fourteen inches in a trough without partitions, filled 
with diluted acid. Although the electrical intensity in this case must 
have been very low, yet there was but little reduction in the apparent 
intensity of the spark. 
* This battery consisted of eighty-eight elements or pairs, composed of plates 
of rolled zine nearly one-eighth of an inch thick, nine inches wide, and twelve 
inches long, inserted into copper cases open at top and bottom. 
