I also know that the use of the opposing piston engines was discontinued in railroad use. While they worked very well in maritime use they couldn't stand up to the grit, grime and pounding of railroad service and were eventually replaced with the standard type diesel engines similar to those in use today. There were also experiments with gas turbine engines. The energy crunch in the early 70's killed that. Also, many cities wouldn't allow them to be brought into the city because of the noise. Union Pacific took one into Los Angeles one time. They never did that again. I remember one time that one had stopped under a highway overpass and the hot exhaust was causing the asphalt roadway to melt. The asphalt fell down into the exhaust stack of the engine which just blew it right back out. That was an expensive lesson. Don't stop a gas turbine under a highway bridge again.