As it came closer, Phaethon saw, within the ice, several concentric shells or spheres of crystalline armor.

Girardieau explained that the thing was structured in a series of concentric shells.

Progress through the final concentric shell was slower and more deliberate than the four they traversed before it.

In place of the concentric shells, he proposed that the heavenly bodies interacted with each other and Earth through magnetic forces.

We came slowly in through the concentric shells of gas that had been blasted out six thousand years before, yet were expanding still.

The natural place of air is likewise a concentric shell surrounding the place of water.

This point becomes center of the concentric spherical shells.

These "concentric shells" (numbered One to Six) each represent different "levels of spiritual being."

Surrounding the ellipsoidal nebula are a series of faint, blue concentric shells.

To show this, we divide the universe into a series of concentric shells, 1 light year thick (say).