ELECTRO-MAGNETIC EXPERIMENTS AND OBSERVATIONS. 479 



III. Zinc West. 



1. Needle applied above, deflected 90° W. 



2. - below, inversion of poles. 



IV. Zinc East. 



1. Needle applied above, deflected 90° E. 



2. - below, deflected to E. ; but varying a 

 little in degree, as moved along the helix. 



Experiments with Left Helix. 



I. Zinc North. 



1. Needle applied above, deflected 



2. - below, 



II. Zinc South. 

 L."_Needle applied above, deflected 

 2. - below, 



III. Zinc West. 



1. Needle applied above, deflected 90° E. 



2. - below, inversion of poles. 



IV. Zinc East. 



1. Needle applied above, deflected 90° W, 



2. - below, deflected to W. ; but varying a 

 little in degree, when moved toward either end of the 

 helix. 



These experiments shew, that the reversed action of right 

 and left helices is chiefly confined to their interior ; for when 

 the zinc is south or north, the outsides of left and right helices 

 act similarly on the needle ; when, however, the zine is west 

 or east, the deflections of the needle are reversed in each sort 

 of helix. The analogy also between the outsides of helices, 



VOL. IX. p. II. 3 p and 



