Unsolid

By this idea of solidity is the extension of body distinguished from the extension of space:--the extension of body being nothing but the cohesion or continuity of solid, separable, movable parts; and the extension of space, the continuity of unsolid, inseparable, and immovable parts.

Source: wiktionary

And equally unsolid is the argument that from a principle of gradation in races would reduce a principle of progress in races.

Source: wiktionary