Si^ 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. 



12. 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 

 i-eference 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 paii's, 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 zinc,' 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 zinc 

 and copper plates of a single pair were separated from each other to 

 the distance of fourteen inches in a trough without partitions, fifled 

 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 zinc nearly one-eighth of an inch thick, nine inches wide, and twelve 

 inches long, inserted into copper cases open at top and bottom. 



