Popular estimation has always credited Prof. Morse with the invention of the telegraph, but to ascribe to him all the praise would do great injustice to many other worthy workers in this field, some of whom are regarded by the best judges to be entitled to equal praise.
The practical telegraph as originally used is resolvable into four essential elements, viz., the battery, the conducting wire, the electro-magnet, and the receiving and transmitting instruments.
The development of the battery began with Galvani in 1790, and Volta in 1800. Galvani discovered that a frog’s legs would exhibit violent muscular contraction when its exposed nerves were touched with one metal and its muscles were touched with another metal, the two metals being connected. The effect was due to an electric current generated and acting with contractile effect on the muscles of the frog’s legs.
FIG. 1.
From this phenomenon, the chemical action of acids upon metals and the production of an electric current were observed, and the voltaic pile was invented. This consisted of alternate discs of copper and zinc, separated by layers of cloth steeped in an acidulated solution. This was the invention of Volta. From this grew the Daniell battery, invented in 1836 by Prof. Daniell of London, quickly followed by those of Grove, Smee, and others. These batteries were more constant or uniform in the production of electricity, were free from odors, and did not require frequent cleaning, as did the plates of the voltaic pile, which were important results for telegraphic purposes. The Daniell battery in its original form employed an acidulated solution of sulphate of copper in a copper cell containing a porous cup, and a cylinder of amalgamated zinc in the porous cup and surrounded by a weak acid solution. In the illustration, which shows a slightly modified form, a cruciform rod of zinc within a porous cup is surrounded by a copper cell, the whole being enclosed within a glass jar.
FIG. 2.—DANIELL’S BATTERY.