<div class="htmlview paragraph">EVERY plow in use should have 10 b.-hp. available. Every tractor engine should deliver continuously at least 33 hp. If the 330-cu. in. engine mentioned were as good as a Liberty airplane engine, it could deliver 57 hp. at 1000 r.p.m. The horsepower actually obtained is as follows:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">41.5</span> <div class="htmlview paragraph">in the laboratory</div> </li> <li class="list-item"> <span class="li-label">33.0</span> <div class="htmlview paragraph">at the factory</div> </li> <li class="list-item"> <span class="li-label">29.0</span> <div class="htmlview paragraph">when burning gasoline</div> </li> <li class="list-item"> <span class="li-label">23.0</span> <div class="htmlview paragraph">when burning kerosene</div> </li> <li class="list-item"> <span class="li-label">21.0</span> <div class="htmlview paragraph">with poor piston-rings</div> </li> <li class="list-item"> <span class="li-label">19.0</span> <div class="htmlview paragraph">with poor spark-plugs</div> </li> <li class="list-item"> <span class="li-label">9.5</span> <div class="htmlview paragraph">available at the drawbar</div> </li> </ol> </div> <div class="htmlview paragraph">The great engineering problem of the future lies between the 57 and the 23 hp. From 19 to 9.5 hp. is the manufacturer's problem. The main difficulties, as outlined by the figures given, lie in the combustion chamber and its ability to dissipate the surplus heat, and in the limitations of fuel. There will be no need for refiners to continue to break up the heavier fuels by processes already so successful, if by ingenuity and good understanding of thermodynamics these can be made to burn in present-day engines.</div>