Page:Handbook for Boys.djvu/132

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Put in a few fresh-water clams and insects in variety, water boatmen, diving spiders, and whirligigs. A tank of beetles will be full of interest. Always add two or three tadpoles as scavengers, and watch their legs grow out as the tail grows short and they become frogs. You can find or buy a variety of turtles which will soon be tame and eat from your fingers. Do not keep turtles with fish.

On every hike or tramp carry a wide-mouthed bottle for specimens and a piece of rubber cloth in which to bring home water plants. Fish can be carried wrapped in damp moss for hours and will be found well and lively when put in the aquarium.

Fish Food

Fish require very little food other than the minute creatures that develop in the water.

The dealers supply proper foods for aquaria, or you can prepare your own. Fine vermicelli is good for gold fish, scraped lean beef is just what the sunfish and Paradise fish want. Ant eggs suit many fish, and powdered dog biscuit will fill many mouths.

It is evident that an article so brief as this is only suggestive. The libraries contain many books of which two are recommended:

"Home Aquarium and How to Care For It." By Eugene Smith, 1902. Published by Dutton, New York.

"Book of Aquatia." By Bateman and Bennett, 1890. Published by L. Upcott Gill, 170 Strand, W. C., London.

United States Geological Survey

Geologists study the materials of the earth's crust, the processes continually changing its surface, and the forms and structures thus produced. In a day's tramp one may see much under each of these heads.

The earth's crust is made up chiefly of the hard rocks, which outcrop in many places, but are largely covered by thin, loose, surface materials. Rocks may he igneous, which have cooled from a melted condition; or sedimentary, which are made of layers spread one upon another by water currents or waves, or by winds.

Igneous rocks, while still molten, have been forced into other rocks from below, or poured out on the surface from volcanoes. They are chiefly made of crystals of various minerals, such as quartz, felspar, mica, and pyrite. Granite often contains large crystals of felsparor mica. Some igneous rocks, especially lavas, are glassy; others are so fine grained that the crystals cannot be seen.

In places one may find veins filling cracks in the rocks and