Page:Heroes of the telegraph (IA cu31924031222494).djvu/111

 into electricity of a more intense nature—into mimic lightning, in fact, with its accompaniments of heat and sound. That entering the signal magnet expends part of its force in the magnetism of the core. That entering the signal coil, which may be taken as the brain of the instrument, appears to us as intelligence.

The recorder is now in use in all four quarters of the globe, from Northern Europe to Southern Brazil, from China to New England. Many and complete are the adjustments for rendering it serviceable under a wide range of electrical conditions and climatic changes. The siphon is, of course, in a mechanical sense, the most delicate part, but, in an electrical sense, the mouse-mill proves the most susceptible. It is essential for the fine marking of the siphon that the ink should neither be too strongly nor too feebly electrified. When the atmosphere is moderately humid, a proper supply of electricity is generated by the mouse-mill, the paper is sufficiently moist, and the ink flows freely. But an excess of moisture in the air diminishes the available supply of exalted electricity. In fact, the damp depositing on the parts leads the electricity away, and the ink tends to clog in the siphon. On the other hand, drought not only supercharges the ink, but dries the paper so much that it insulates the siphon point from the metal tablet and the earth. There is then an insufficient escape for the electricity of the ink to earth; the ink ceases to flow down the siphon; the siphon itself becomes highly electrified and agitated with vibrations of its own; the line becomes spluttered and uncertain.

Various devices are employed at different stations to cure these local complaints. The electrician soon learns to diagnose and prescribe for this, his most valuable charge. At Aden, where they suffer much