90 THE ELECTRIC TELEGRAPH. 



Private message . . . . . 



CaU . . . .'...; ..._. 



Understood . . . . .' ^ 



Interruption 



Conclusion 



Wait .... . . . _... 



Receipt B 



The length of a dot being taken as a unit, the length of 

 a dash = 3 dots. 

 The space between the signs composing a letter = 1 dot. 



letters = 3 dots. 



words = 6 dots. 



The formation of the numerals is ingenious ; they are 

 each represented by five of the two elements, and so that, 

 disregarding the dashes which stand on the right hand, and 

 giving a value of unit to a dot and two to the dashes on the 

 left, the value of the numeral represented is expressed. 



The signs of punctuation, official signals, &c., are either 

 higher variations or arbitrarily chosen letters of the alphabet 

 whose single appearance is a sufficient indication that they 

 are not to be construed as forming parts of words. 



62. Morse's Transmitting Plate. Soon after Morse's inven- 

 tion of the transmitting key his attention was directed to the 

 fact that some people find great difficulty in manipulating 

 the arbitrary combinations with uniformity in the length 

 of the marks and spaces. He, therefore, constructed an 

 arrangement for facilitating the transmission. On a metal 

 plate, B B, Fig. 46, are soldered series of raised rectangular 

 pieces of metal, whose lengths and distances apart correspond 

 with the arrangement of the Morse alphabet. Between these 

 pieces, strips of ivory of equal thickness are inlaid, making 

 the whole surface, A A, level. These metal pieces are shown 

 black in the figure and the ivory white. From a binding 

 screw, c, attached to the plate B B, and therefore in electrical 

 connection with each of the metallic rectangles, a wire, 

 m, is led to the receiving instrument and a battery, the further 



