Page:Popular Science Monthly Volume 18.djvu/500

484 in this country and Europe, and in both rapidly going into use, we have a machine that is a very satisfactory solution of the problems involved in the construction of this class of motors. In the matter of fuel it is nearly, if not quite, as economical as a steam-engine of corresponding power, and is, therefore, in actual use much more so, both



because no engineer is required to run it and the expense of keeping up steam, whether running or not, is avoided. The combustible charge introduced into the cylinder is composed of gas and air in such proportions that rapid combustion instead of an explosion takes place, and, to obtain sufficient pressure from its expansion, it is compressed to one third its original volume before being ignited.