With these new devices for increasing the power of the oscillations, or in other words throwing a bigger stone into the pond, the electrical waves are sent out with far greater force, just as the water waves are sent farther in the pond, and will reach stations at a greater distance. "Crash, bang," goes the oscillator, and in less time than it takes to think it the oscillations have reached the antennæ of ships hundreds or thousands of miles away, or even those of another land station on the other side of the Atlantic Ocean. The next thing is to understand the apparatus used for receiving the faint electric waves transmitted through the ether, for the modern instruments are far different from the old style "coherer" explained before. As with the spark gaps, there are many different styles of receiving devices, all known by the general name of "detectors," as they detect the faint electro-magnetic waves radiating through the ether. Some of the latest Marconi experiments show a return to the "coherer" idea, very greatly improved upon, but the full details of the device have not been made public. [Illustration: Courtesy of the New York Edison Co. THE NAVY WIRELESS SCHOOL At top is the class in sending, while below is shown the class learning to receive messages.] [Illustration: AN AMATEUR WIRELESS OUTFIT Hundreds of boys are receiving and sending wireless messages with far less efficient apparatus than that shown here.] [Illustration: MARCONI DETECTOR LAYOUT A--Aerial. B--Condenser. C--Glass tube oscillator transformer. D--D´--Rollers. E--E´--Iron wire passing through oscillator transformer. F--F´--Magnets. G--G´--Ground wires. H--Telephone receiver.] One of the detecting devices used by the Marconi system, after the old-style "coherer" was done away with, was very simple indeed in comparison to the cohering and tapping machines. It was made up of a small glass tube wound with copper wire. One end of this made the ground connection, and the other end led to the aerial, and also to an earth connection through a tuning inductance coil. Then another coil was wound around the first one on the glass tube and connected with the head telephone receivers which have taken the place of the Morse dot and dash printing instrument in all the modern wireless instruments. Two magnets were placed just above the glass tube, and a flexible iron wire was made to move through it by means of a pair of rollers a little way from each end. When the electro-magnetic waves reached the aerial and made oscillations in the first coil about the glass tube, the magnetic intensity of the iron wire band was disturbed and the glass tube became an oscillation transformer, setting up currents in the coil leading to the telephone receivers. The impulses were manifested by ticks, just the length of the dots and dashes being sent out by the operator perhaps thousands of miles away.