Mirages and tricks of the eye

In the heat, the air near the ground becomes much hotter than the air above and bends the light. That is how a mirage appears: what looks like a shimmering lake on the horizon is actually a reflection of the sky. It happens mostly on flat terrain and during the hottest hours.

• Do not chase "water" on the horizon if it is on flat terrain and seems to move or recede.
• Distances deceive. In the dry, clear desert air, a mountain 20 miles away can look like it is 5. Multiply your first estimate and do not set out on foot toward a "nearby" point without enough water.
• Look from a high point or at dawn and dusk, when the mirage fades.
• Real water in the desert gives itself away by green vegetation (cottonwoods, reeds, willows), birds flying toward one spot at dusk, or animal trails that converge (chapter 3).