1838] WRITINGS OF JOSEPH HENRY. 117 



whole length was wound on the iron of a temporary magnet 

 no shocks could be obtained. The wire of the machine may 

 therefore be of such a length, relative to its diameter, as to 

 produce shocks, but no decomposition; and if the length be 

 still further increased, the power of giving shocks may also 

 become neutralized. 



36. The inductive action of coil No. 1, in the foregoing 

 experiments, is precisely the same as that of a temporary 

 magnet in the case of the magneto-electrical machine. A 

 short thick wire around the armature gives brilliant defla- 

 grations, but a long one produces shocks. This fact, I be- 

 lieve, was first discovered by my friend Mr. Saxton, and 

 afterwards investigated by Sturgeon and Lenz. 



37. We might, at first sight, conclude, from the perfect 

 similarity of these effects, that the currents which, according 

 to the theory of Ampere, exist in the magnet, are like those 

 in the short coil, of great quantity and feeble intensit}^; but 

 succeeding experiments will show that this is not necessarily 

 the case. 



88. All the experiments given in this section have thus far 

 been made with a battery of a single element. This condi- 

 tion was now changed, and a Cruickshanks trough of sixty 

 pairs substituted. When the current from this was passed 

 through the ribbon coil No. 1, no indication, or a very feeble 

 one, was given of a secondary current in any of the coils or 

 helices, arranged as in the preceding experiments. The 

 length of the coil, in this case, was not commensurate with 

 the intensity of the current from the battery. But when 

 the long helix, No. 1, was placed instead of coil No. 1, a 

 powerful inductive action was produced on each of the 

 articles, as before. 



89. First, helices No. 2 and 3 were united into one, and 

 placed within helix No. 1, which still conducted the battery 

 current. With this disposition a secondary current was pro- 

 duced, which gave intense shocks but feeble decomposition, 

 and no magnetism in the soft iron horseshoe. It was there- 

 fore one of intensity, and was induced by a battery current 

 also of intensity. 



