HISTORY AND PROGRESS. 



31 



Thus, on lifting the coil a a, if we suppose a deflection of the 

 magnet was produced to the right, by reversing the commu- 

 tator and then lowering the coil again, another deflection in 

 the same direction would be observed. To produce a third 

 deflection in the same direction it would be necessary, evi- 

 dently, to reverse the commutator again before raising up 

 the inductor. After this fashion Gauss and Weber were 

 enabled, by an ingenious combination of deflections to the 

 right and left, to form the following alphabet and numerals 

 with a maximum of four elementary signals in a letter : 



r represents the swing of the north pole of the magnet 

 towards the right, and / the swing of the same pole towards 

 the left of the magnetic meridian. 



Various lengths of the pauses between the signals indicated 

 the conclusion of words and sentences. 



The copper frame around the needle was necessary in order 

 to prevent the great number of oscillations which the magnet 

 would have made across the meridian had no such check 

 been introduced. 



The checking action of masses of metal in the vicinity of 

 an oscillating magnet was discovered by Arago, and has 

 been described by Sir William Snow Harris,* in whose ex- 

 periments the oscillations of a freely suspended magnetic 

 needle were reduced from 420 without a damper, to 14 with 

 a damper of copper surrounding the needle. 



In the case of the magnet used by Gauss and Weber, its 

 mass, and the minuteness of the angle which was necessary 

 for the deflection to be read off with the aid of the telescope 

 and mirror, must have assisted materially in bringing it back 

 to the meridian line. 



* "Magnetism," p. 58 ; " Phil. Trans.," 1831, Part I. 



