Of course, 1938's engineers understood that intermeshing propellers must be driven by a single engine. But could I reveal the UB-38RAA-4 (and -5 and -6), top secret, that saved Australia from invasion? Well, maybe in 2013 we should do it, let's go:
(the UB-38RAA-6 is a twin-engined plane, with its port engine driving the push-propellers and its starboard engine driving the pull-propellers)