might be metal in the volcanic ground—created by dusting ground mica on wet glue to catch the reflection of the sun. It was a masterpiece.

The sun. Black sky holding a giant, blazing ball. Too damned yellow, but filtered carbon arcs were the best we could do.

Down, into the tunnel that was lock two. This next one ... Venus, obvious opposition point of attack, where we'd had the most trouble: Venus had to be right.

It was! A blast of wind struck us, and dust, swirling everywhere. We'd discovered there's no such thing as a sand storm—it's really dust—so we'd taken pains making things look right. Sand dunes were carefully cemented in place; dust rippling over gave the proper illusion.

Oddly shaped rocks, dimly seen, strengthened the impression of wind-abraded topography. Rocks were reddish, overlain by smears of bright yellow. Lot of trouble placing all that flowers of sulfur, but we postulated a liquid sulfur-sulfur dioxide-carbon dioxide cycle.

Overhead, a diffused, intense yellow light. The sun—we were on the daylight side.

I sighed, relaxed, knowing this one had worked out.

We gave the moon little time. For those who had become homesick, Earth was hanging magnificently in the sky. At a crater wall, we stopped, ostensibly to let souvenir hunters pick at small pieces of lunar rock without leaving the cart.

We'd argued hours on what type to use, till Mel dragged out his rock book. Most, automatically, had wanted basalt. However, the moon's density being low, heavier rocks are probably scarce—one good reason not to expect radioactive ores there. We finally settled for rhyolite and obsidian.

Stopping on the moon had another purpose. We kept the room temperature at 70 F, for heating and cooling economy; the transition from Venus to Mars was much simpler if ambient temperature dropped from 140 to 70 and from 70 to 0, rather than straight through the range.

Next, a Martian polar cap, and we looked down a long canal that disappeared on the horizon. Water appeared to run uphill for that effect. The whole scene looked like an Arizona highway at dusk—what it should have. To our right, a suggestion of—damn the opposition's eyes—culture: a large stone whatzit. It was a jarring note.

We selected one of those nondescript asteroids with just enough diameter to show extreme 

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