I obediently brought another grain of sand.

“Higher!”

I silently added five smooth stones.

“Oh, build it up!” she begged. “You ought to see the slant.”

I pried a large boulder from the ledge and balanced it on the rail.

“Your rail's breaking!” cried my mother, so suddenly that I lost my footing.

I seized the leg of the tripod in one hand, the branch of a tree with the other, while the flying buttress went rumbling down the defile, and I was left clinging to the bare rock, that refuge of the wild goat.

We have now some very attractive pictures of the Den, taken from a spot where no tripod was ever pitched before, and where I hope no tripod will be pitched again. But as we developed the plates that night, I told Barbara that I did not think that I was qualified to help her much about the camera any more.

“You were all right,” said she kindly. “It was the mosquitoes.”

And I was mollified by this as perhaps I could have been by no logic in the world.