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BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



directions the reverse of what they were at first, and hold- 

 ing the ring in one hand, let us again introduce the magnet 

 into it with the other hand, until it is half-way through ; 

 the slightest change in this position causes it to move with 

 an accelerated velocity towards that pole which is nearest to 

 it ; and getting entirely clear of the magnet, it is projected 

 to a considerable distance from it. At length, however, it 

 stops, and, gradually turning round, presents the opposite 

 face to the magnet ; attraction now takes place, and the 

 ring returns to the magnet with a force equal to that with 

 which it had before fled from it ; and passing again over 

 its pole, finally rests in its position of equilibrium, encircling 

 the middle, or what may be termed the equator of the mag- 

 net. In the former position it was equally attracted by the 

 two poles of the magnet : in the latter it is equally repelled. 



Price, $1.00. 



Fig. 42-2. Improved form of De la Rive's JRinff.(Fig. 

 422.) Another and preferable form of the same 

 instrument, in which the motions are less imped- 

 ed, consists in its being set afloat in a little glass 

 bowl, and the voltaic pair placed in a horizontal 

 position ; the whole is then set afloat in a large 

 basin of water, and on pouring a little dilute 

 sulphuric acid into the bowl, the coil will be 

 surprisingly sensible to the influence of a magnet, and will 

 be attracted and repelled at a distance of several inches. 



Price, $1.25. 



Fig. 423. Floating CW. (Fig. 423.) 



A simple galvanic apparatus, 

 which when placed in acidulated 

 water turns spontaneously, so as 

 to place itself north or south, or 

 accordant to the magnetic meri- 

 dian. It consists of a coil of wire, 

 the ends of which are brought 

 through the coil, and are terminated by two pieces of metal, 

 about an inch square each ; one plate being of zinc, the 

 other of copper. When this instrument is in use, it is ne- 

 cessary to suspend it by a thread, or support it by a cork 

 at each end, lest it should sink. Price. $1.00. 



