More important than mere foods, the presence or absence of these invisible substances was now generally believed to confer health benefits on their eaters.

Dark matter is the mysterious, invisible substance that hugs galaxies and makes up around a quarter of the universe.

Or, was there some invisible substance to them that his untutored eyes were failing to grasp?

The rest is formed from an invisible substance called "dark matter".

Set in it was a window of some almost invisible substance, supporting a stylus which passed vertically through it.

The arm moves over the head as if to pour on the right face and body an invisible substance (fig. 364).

Air, too, I must learn to accept for the invisible substance that it is.

Magic dust - invisible substance stored in magician's pocket that supposedly makes tricks work.

He seemed to be gathering some invisible substance from the arm of his chair with his right hand, and depositing it in his left.

The invisible substance that was Ninidh shrieked in outrage.