342 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
layer at about 1,800 feet. To cause this mirage, the layer between 
Picacho and Yuma must have been fairly strong, with the elevation 
well over 2,000 feet. 
It has been my observation that “mirage showmen” are very partial 
toward the No. 2 lenses for morning exhibitions and No. 1 for after- 
noon displays. Generally, too, a brisk wind is unfavorable for forma- 
tion of a mirage-making lens aloft, having a decided mixing effect. 
But there are exceptions. One particular production was staged 
about midafternoon in a brisk 12- to 15-mile-an-hour wind. Scattered 
desert brush and scrub trees had been assembled and lined up with 
looming effect to look like a row of trees, as though along a fence 
or road, 25 to 30 feet high. Looming trees are not unusual, but the 
scattered, scrubby material the mirage makers had to work with was 
exceptional. It was a nice-looking row of trees. As an added fea- 
ture, the lively east wind snatched the west end of the row, two or 
three trees, and whirled it away 30 to 40 yards where it disappeared 
in complete fragmentation and instantly reappeared back where it 
belonged in the row. This happened over and over again as long 
as we watched. It reminds one of the lens in the road, steadfast in 
the wind and hurrying traffic. I have had other reports of wind 
disturbance by No. 1 lenses, but this is the only case I know of for a 
No. 2. 
The following example defies classification: Just across the United 
States-Mexico boundary in Baja California there used to be a shallow 
salt lake known as Laguna Salada nearly filling a valley between 
the Coast Range and Cocopah Mountains. It had long been fed, 
through its southern end, by high tides from the Gulf of California 
and overflow from the Colorado River at times of flood, helped by 
some mountain runoff. A shift of the river channel following a 
break into the Salton Sea in 1904 silted up the entrance, and the 
lake slowly dried up in spite of local runoff. Visiting Laguna Salada 
in 1925, we topped the pass south of Signal Mountain to get an excel- 
lent view of the lake bed, dry and dazzling white except out toward 
the center where there was a little blue body of water. Water is 
almost always an appealing sight in our desert country, so we drove 
to the north end of the Laguna, walked down a gently sloping beach 
littered with seaweed and shells, then dropped steeply 7 or 8 feet 
to the level floor, intending to walk out. But from there no lake 
was visible—some strips of what was evidently mirage water in the 
distance but nothing that looked like real water. Apparently we had 
been well fooled. Climbing out, there was our lake again. As we 
walked south along the ridge it was still visible from the pass in the 
same place and of the same size and shape. Studying it with binocu- 
lars, we could see no sign of ripples, but it looked very real. So I left 
