MAGNETIC INSTRUMENTS. 



Magnetic Dirks, Arma- Fig. 418. 



tyres, &c. (Fig. 418.) 

 1. Circular and Star Discs, 

 of soft plate iron, for illus- 

 trating the distribution of 

 magnetism on ferruginous 

 bodies. When the pole of a 

 magnet is placed on or near 

 the centre of the discs, the 

 extremities exhibit dissimi- 

 milar polar states to that developed at the centre. 



Price, 50 cts. 



2. Soft iron Cylindrical Armature, which, when placed 

 upon an inclined horse-shoe magnet, descends by its own 

 weight, rolls over the face, and partially ascends again on 

 the under side. Price, $1.00 and $2.00. 



3. Flat Steel Bars, straight and circular, to illustrate the 

 effect of division and fracture in the distribution of mag- 

 netism. When the magnetic bars are suddenly separated in 

 the centre, or a portion broken off from either end, each 

 piece will be a complete magnet. Price, 12 Jets, and 25 cts. 



4. Slender Cylindrical Rods and half links to form a chain 

 of soft iron of various dimensions, to illustrate that inductive 

 influence* renders soft iron a temporary magnet, while in ap- 

 proximation with a permanent steel magnet. 



Price, per dozen, 25 cts. and 50 cts. 



5. Armature consisting of a cioss bar of soft iron, which, 

 when attached by attraction to the pole of a permanent 

 magnet, suspends soft iron balls at each end of the bar, and 

 exhibits a pleasing variety in magnetic inductive phenomena. 



Price, 75 cts. 



6. Iron balls polished. Price, each, 25 cts. 



7. Robinson's forked or Y shaped soft iron armature, for 

 demonstrating the neutralization or destruction of induced 

 magnetism, by two equal and opposite magnetic actions. 

 If one branch be suspended to a pole of a horse-shoe mag- 

 net, the lower end of the fork will attract and support a 



