There is no reason for supposing that the ether ought to be a sort of extension of the bodies we are accustomed to handle.

Its properties may astonish our ordinary way of thinking, but this rather unscientific astonishment is not a reason for doubting its existence.

Real difficulties would appear only if we were led to attribute to the ether, not singular properties which are seldom found united in the same substance, but properties logically contradictory.
In short, however odd such a medium may appear to us, it cannot be said that there is any absolute incompatibility between its attributes.
It would even be possible, if we wished, to suggest images capable of representing these contrary appearances.

Various authors have done so.
Thus, M.Boussinesq assumes that the ether behaves like a very rarefied gas in respect of the celestial bodies, because these last move, while bathed in it, in all directions and relatively slowly, while they permit it to retain, so to speak, its perfect homogeneity.
On the other hand, its own undulations are so rapid that so far as they are concerned the conditions become very different, and its fluidity has, one might say, no longer the time to come in.

Hence its rigidity alone appears.
Another consequence, very important in principle, of the fact that vibrations of light are transverse, has been well put in evidence by Fresnel.