478 ELECTRO-MAGNETIC EXPEBIMENTS AND OBSERVATIONS. 



IV. Zinc East. 



1. Needle in its axis, deflected 90° E. 



2. - above, deflected E. 



3. - below, not deflected, but strongly acted on. 

 The sides of this cylindric tube shewed no action, except 



when the needle was moved toward the upper, or under part 

 of the tube, when it partook more or less of the action pecu- 

 liar to that surface. 



The electro-magnetic effects of the outside of the cylindri- 

 cal tube, appear to differ in no respect from those of rectangu- 

 lar connecting pieces, or common connecting wires. When a 

 needle is introduced in its axis, and is deflected at all, that de- 

 flection partakes, more or less, of the direction it assumes, 

 when applied to the upper surface of either ; but the degree of 

 deflection appears to be subject to sudden variations and irre- 

 oularities, of which the cause was not always apparent. If we 

 may be allowed the expression, it seemed as if the electro- 

 magnetic current moved through the tube with difficulty. 



Finding the outside of the tube giving such decided electro- 

 mao'netic indications, we examined the action of the outside of 

 the helices. 



Experhnents "with Right Helix. 



I. Zinc North. 



1 . Needle applied above, deflected 90° E. 



2. - below, - 90* W. 



II. Zinc South. 



1. Needle applied above, deflected 90° W. 



2. - below, - 90° E. 



III. Zinc 



