We lightered it, set up the tent, and as it was now but a short hour to sundown I bade them leave me and make their search.

They went off together, and I busied myself with opening some of the paraphernalia I had brought with me.
First of all I took out the two Becquerel ray-condensers that I had bought in Sydney.

Their lenses would collect and intensify to the fullest extent any light directed upon them.

I had found them most useful in making spectroscopic analysis of luminous vapours, and I knew that at Yerkes Observatory splendid results had been obtained from them in collecting the diffused radiance of the nebulae for the same purpose.
If my theory of the grey slab's mechanism were correct, it was practically certain that with the satellite only a few nights past the full we could concentrate enough light on the bosses to open the rock.
And as the ray streams through the seven globes described by Throckmartin would be too weak to energize the Pool, we could enter the chamber free from any fear of encountering its tenant, make our preliminary observations and go forth before the moon had dropped so far that the concentration in the condensers would fall below that necessary to keep the portal from closing.
I took out also a small spectroscope, and a few other instruments for the analysis of certain light manifestations and the testing of metal and liquid.

Finally, I put aside my emergency medical kit.
I had hardly finished examining and adjusting these before O'Keefe and Huldricksson returned.