A slow, steady light, growing more and more bright, and changing in colour from blue to crystal white.

So they stayed for a couple of minutes without change in the coffer; till at last there began to appear all over it a delicate glow.

This grew and grew, till it became like a blazing jewel, and then like a living thing whose essence of life was light.
We waited and waited, our hearts seeming to stand still.
All at once there was a sound like a tiny muffled explosion and the cover lifted right up on a level plane a few inches; there was no mistaking anything now, for the whole room was full of a blaze of light.

Then the cover, staying fast at one side rose slowly up on the other, as though yielding to some pressure of balance.

The coffer still continued to glow; from it began to steal a faint greenish smoke.
I could not smell it fully on account of the respirator; but, even through that, I was conscious of a strange pungent odour.