96 WRITINGS OP JOSEPH HENRY, [1835 



by a bubble of gas given off at each wire. It must be recol- 

 lected that the shocks and the decomposition here described 

 were produced by the electricity from a single pair of plates. 



11. The contact with the poles of the battery and the large 

 spiral being broken in a vessel containing a mixture of 

 hydrogen and atmospheric air, an explosion was produced. 



I should also mention that the spark is generally attended 

 with a deflagration of the mercury, and that when the end 

 of the spiral is brought in contact with the edge of the cop- 

 per cup or the plate of the battery, a vivid deflagration of the 

 metal takes place. The sides of the cup sometimes give a 

 spark when none can be drawn from the surface of the mer- 

 cury. This circumstance requires to be guarded against 

 when experimenting on the comparative intensities of sparks 

 from different arrangements. If the battery formerly de- 

 scribed [fig. 1, page 81] be arranged as a "calorimotor," and 

 one end of a large spiral conductor be attached to one pole, 

 and the other end drawn along the edge of the connector, 

 fig. 4, a series of loud and rapid explosions is produced, ac- 

 companied by a brilliant deflagration 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 reference to the shock, the spark, &c.; but 

 no difference could be observed with the large spiral con- 

 ductor; the effect of the iron was merged in that of the spiral- 

 When however one of the smaller ribbons 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 in- 

 serted, the spark appeared a little more intense than without 

 the iron. The obliquity of the spires in this case was un- 

 favorable 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 re-action on each other of the several spires of the 

 coil which surround the magnet. 



