Question on fossils/rock formations that look like engine parts

I'm trying to read an old family journal and in it is written that in 1839 this fellow found what he thought was 'parts, gears and pipes from a rusted steam engine' this might be true but it was near Aden in Arabia some fifteen miles inland out in a rocky desert and I suspect no steam engine would be there at that period of time. I suspect he saw some sort of rusty looking stone formation or collection of fossils. Any ideas of what kind of rock formation or fossils might look like 'parts, gears and pipes'?

Thanks