The compact little two-cycle motors represent another big fundamental development in the field of gas engines. There are many different makes of two-cycle motors, of course, and all have their various merits. They are used in practically all the work for which gas engines are employed, including automobiles, motor boats, and aeroplanes. It will not be necessary to describe these engines further than to say that the name describes the fundamental difference between them and the four-cycle motors. Instead of the piston making four strokes for every explosion--that is, an, upward stroke to clean out the burnt vapours, a downward stroke to suck in the fresh gas, an upward stroke to compress it, and finally the downward explosion or power stroke, all this work is done in two strokes. For the general development of the gasoline engine, it is only necessary for a boy to look about him. Everywhere motors built on the same ideas as laid down in earlier inventions, but improved in every detail, are in use. Not only do we see them on fine pleasure automobiles, motor boats, and aeroplanes, but on our biggest trucks, fire engines, and in business establishments where light machinery is to be run. CHAPTER XI THE WIRELESS TELEGRAPH UP TO THE MINUTE THE SCIENTIST TALKS OF AMATEUR WIRELESS OPERATORS--THE GREAT DEVELOPMENT OF WIRELESS THAT HAS ENABLED IT TO SAVE ABOUT THREE THOUSAND LIVES--LONG DISTANCE WORK OF THE MODERN INSTRUMENTS While the inspiring stories of Jack Binns of the steamship _Republic_, and of J. G. Phillips and Harold S. Bride of the ill-fated _Titanic_ are fresh in our minds, it is not necessary to say that within the last few years the wireless telegraph has established itself as indispensable to the safe navigation of the seas. The story of its development is a marvellous one when we think that it was only in December of 1901 that Marconi received the first signal ever transmitted across the Atlantic Ocean without wires. Now, as every boy knows, all the big steamships are equipped with wireless, all the governments of the world operate their own stations to communicate with their warships, at sea, and thousands upon thousands of boy amateurs operate their own little plants with complete success. More wonderful still is the story when we think that by the use of this invention a total of about three thousand persons have been saved from death in shipwrecks. Nowhere in the pages of all history are there any more thrilling stories of heroism and devotion to duty than those of the men who, in the face of death themselves, have stuck by their keys sending out over the waves the "C. Q. D." and the "S. O. S." signals, which as every boy knows are the wireless calls for help.