6 CONTRIBUTIONS TO ELECTRICITY AND MAGNETISM. 



beginning was constantly increased. We may therefore state generally, that, 

 at the beginning of the battery current, the induction of a unit of its length is 

 increased by every diminution of the length of the conductor. 



13. In the experiment given in paragraph 11, the intensity of the shock at 

 the ending of the battery current diminishes with each diminution of the length 

 of the coil ; and this is also due to the decrease of the number of the spires of 

 the coil, as is evident from an experiment similar to the last, in which the helix 

 was placed on a coil consisting of only two turns or spires of copper riband; 

 the shock at the ending, with this arrangement, was comparatively feeble, but 

 could be felt in the hands. Different lengths of coil No. 2 were now intro- 

 duced into the same circuit, but not so as to act on the helix; but although 

 these were varied from four or five feet to the whole length of the coil, (sixty 

 feet,) not the least difference in the intensity of the shock could be perceived. 

 We have, therefore, the remarkable result, that the intensity of the ending in- 

 duction of each unit of length of the battery current is not materially altered, 

 at least within certain limits, by changing the length of the whole conductor. 

 From this we would infer that the shock depends more on the intensity of the 

 action than on the quantity of the current, since we know that the latter is di- 

 minished in a given unit of the conductor by increasing the length of the 

 whole. 



14. We have seen (8) that with a circuit composed of ten elements of the 

 compound battery and'the coil No. 2, the shock, at the beginning of the cur- 

 rent, was fully equal to that at the ending. It was, however, found that if, in 

 this case, the length of the coil was increased, this shock was diminished; and 

 we may state, as an inference from several experiments, that however great 

 may be the intensity of the electricity from the battery, the shock at the be- 

 ginning may be rendered scarcely perceptible by a sufficient increase of the 

 length of the primary circuit. 



15. It was also found that when the thickness of the coil was increased, the 

 length and intensity of the circuit remaining the same, the shock at the 

 beginning of the battery current was somewhat increased. This result was 

 produced by using a double coil; the electricity was made to pass through one 

 strand, and immediately afterwards through both : the shock from the helix in 

 the latter case was apparently the greater. 



16. By the foregoing results we are evidently furnished with two methods 



