Page:Electricity (1912) Kapp.djvu/106

and also in the process of laying submarine cables, that some apparatus for producing strong electrification is required. This need arises in connection with a receiving instrument known as the syphon recorder. If a permanent record of the telegraphic message is desired, the receiving apparatus itself must write down this message, not in actual letters, but in certain telegraphic code signs on a moving strip of paper. To use a pen in touch with the paper is out of the question, because the mechanical force exerted by the mechanism of the receiving telegraph instrument is, with the feeble electric currents that can be got to pass through a submarine cable, too small to overcome the friction between paper and pen. In order to allow the pen to move unfettered and write freely it must not touch the paper. This is done by using for a pen a capillary glass tube and electrifying the ink. We have then a conductor, namely, the ink, with a fairly sharp point, namely, the capillary end of the tube. It was shown above that the force which causes electricity to flake off from a conductor is very great at a sharp point, and thus the electricity dispersing from the end of the tube takes the ink with it, thus squirting it against the paper. In this manner the slight