Page:Popular Science Monthly Volume 89.djvu/110

96 the swiftest current, and in rapids between stones. Sometimes they are found in great numbers along the brink of a waterfall. The observer must look carefully to see the net, as it is usually obscured by the dirt that collects and adheres there in little masses. But if he is so fortunate as to find one recently completed, the net-like formation is clear and beautiful.

In some places empty cases may be seen at the edge of the brook. Often they almost completely cover the rocks and the earth between them. In such instances the insects have emerged at the time of a freshet and the retreating water has left the cases stranded high and dry. The two empty cases here illustrated were obtained in this manner. They were selected from a large number because they are perfect examples of what the mason calls ashlar work, that perfect fitting together of stones without packing. Common as are the caddis worms and as often as they have been observed, not a single one has had its life history recorded in this country. A fascinating field for original investigation is here open to the first comer. Endeavor along this line is sure to be interesting.

HE BIG TOP" is the circus man's term for the main tent with the three rings. One of these huge spreads of canvas has been taken over by a Los Angeles dealer in used cars to sell everything propelled by motors.

The tent will hold five thousand people, and it has a display capacity of five hundred cars, trucks and "jitneys." There is an oval track one eighth of a mile in circumference, and the machines go whizzing about this as if it were an indoor speedway contest. The crowd looks on from the central enclosure and judges the merits of the used cars by what they can do—not by fresh paint and varnish.

An additional test is afforded In' the twenty per cent incline in the center of the arena. Here the car shows what it can do on a grade. This platform is also used as an auction block for crowded twice-a-week sales. The machine whirls about the track, runs up the incline to the elevation well above the heads of the spectators, and is then knocked down to the highest bidder.

Private sales continue all through the week. A dozen salesmen are employed.