Imponderable [adjective]

There were, Caro said, regions of ether too subtle to sustain even so imponderable a poet as Mr. Prothero.

Every letter which came from the absent sister did inclose some imponderable unmounted photograph, with comments.

We are in the present day upon the trace of a great many important facts relating to the imponderable agencies employed in nature.

Is or is not that which is called magnetic effluvia a something, a stuff or a substance, invisible and imponderable though it be?

It had simply affected his imagination, which was a consequence of the imponderable sort.

The study of ether, or imponderable matter, pertains principally to physics.

The moon appeared just clear of the lofty parapet of the well, and poured down to us an imponderable rarity of bluish fire.

So mental action may be imponderable, intangible, and yet a real existence, and ruled by the Eternal through his laws.

Justine Brent had one of those imponderable bodies that seem a mere pinch of matter shot through with light and colour.

Confirmatory evidence that energy is a molecular motion and not an "imponderable" form of matter accumulated day by day.