Schauberger
At first this proposal was ridiculed, because according to expert opinion either the ore, having a specific weight of 1.9 and therefore heavier than water (= 1.0), would be left lying on the bottom or the pipe-walls would be heavily scoured within a short space of time, and therefore the proposal would not be commercially viable. [The Energy Evolution - Harnessing Free Energy from Nature, The Transport of Ore in Double-Spiral-Flow Pipes]