Definition of "sheerly"

On a sheerly technical plane, the projections used for the backgrounds were very effective, particularly in the third act, where a sunset faded most convincingly.

1988 October 21, George Grass, “WagnerVision”, in Chicago Reader‎

The pit dropped sheerly from my feet, but a little way along, the rubbish afforded a practicable slope to the summit of the ruins.

1898, H.G. Wells, The War of the Worlds, London: William Heinemann, page 238