HISTORY AND PROGRESS. 41 



his constructions and subsequent experiments he was much 

 indebted to the valuable aid of a fellow-passenger, Dr. Jack- 

 son, of Boston, who had witnessed in Paris numerous experi- 

 ments in telegraphy, and was besides versed in both electricity 

 and chemistry. t 



The first invention made by Morse was a chemical tele- 

 graph by the decomposition of acetate or carbonate of lead, or 

 turmeric moistened in a solution of sulphate of soda on 

 paper, by the galvanic current between platinum points. 



Morse proposed to work this telegraph by means of types 

 forming a code of the letters of the alphabet, numerals, &c., 

 to be set up in a sort of composing stick, and passed by 

 mechanical means under a lever carrying a contact breaker, 

 which would rise and fall correspondingly to the forms of 

 the types. On arriving at New York, Morse took steps to 

 get a set of types for his proposed telegraph, but was, it is 

 said, prevented by press of business from doing much with 

 it until 1836. In the mean time he gave up the idea of a 

 chemical receiving apparatus, and determined on the adop- 

 tion of electro-magnetism. 



41. Morse's telegraph underwent, in the few following 

 years, many important modifications. An idea may be 

 formed of how different the later arrangements of Morse's 

 apparatus were from the first, from the fact that the electro- 

 magnets of the latter weighed 158 pounds, and that two 

 men were necessary to lift it with its stand. The bobbins of 

 the wire coils were 3 inches long and 18 inches diameter, 

 and the iron core nearly 1 inch. Morse used No. 16 copper 

 wire insulated with a coating of cotton threads, it being at 

 that time his opinion that the coil should be made of the 

 same sort of wire as that used for the line. 



The transmitting key used by Morse in his later apparatus 

 is shown in Fig. 21. It consisted of a lever turning on the 

 axis, supported by uprights which were screwed into a small 

 block of dry wood. The screw on the longer arm of the 

 lever was pressed upon the front contact, whilst the similar 

 screw in the shorter arm was used only to regulate the play 

 of the key. 



