A LOOK AT A POP-UP BOOK

I know some books that have secrets buried between the pages. They are chubbier than your garden-variety book, and they ask you to do more than just read. You might have to pull a lever or turn a page. And they are not so much written as they are engineered. These paper masterpieces are movable and pop-up books. The pictures are often complex - designed with moving parts or three-dimensional figures. There are some of your favorite Saturday morning TV cartoon superheroes, classics like Beatrix Potter's ``Peter Rabbit,'' or Jules Verne's ``20,000 Leagues Under the Sea'' - complete with an octopus whose long green tentacles jump out to grab you.

Mechanical or movable books have been around a long time (even if Saturday morning superheroes haven't). In fact, they were used long ago to help people understand how the sun and stars moved, or how the human body worked. Children used to save their pennies a long time to buy one.

Take the book in the picture at the left, for instance. This shows the famous ``International Circus'' that was first put together by Lothar Meggendorfer of Germany in 1887. When completely spread out, the circus is over five feet long. See how many people you can count. There is a daring horseback rider and aerialist, two clowns tussling with a donkey, Chinese acrobats, and crowds oohing and ahing in the background. On the underside of each picture is a little poem about the performer.

Meggendorfer was born in 1847. When he was 19, he worked on the staff of a humor magazine, where he drew comic pictures and wrote silly rhymes that were popular. He loved children, and his first movable book was a Christmas present for his son. Although no one knows for sure, Meggendorfer is said to have created at least 200 movable books. He is considered a great inventor, and antique copies of his books are much sought after by collectors.

Meggendorfer was particularly good at caricatures - which means he drew funny pictures of people that exaggerated their appearance. Cartoons are caricatures. In the middle of this newspaper, on the Editorial Page, there is often a political cartoon that will show a caricature of President Reagan or somebody famous. You can see that the artist chooses parts of that person that stand out, and emphasizes those features. It could be eyebrows, or hair, or ears, or mouth. That way, you can recognize the person, but it's a funny distortion of the way he looks. (You and your brother or sister could try to draw a caricature of each other, and then see if you recognize yourselves.)

Meggendorfer's movable books were special for two reasons. The first was the caricatures he drew, and the second was the way he made them move. The secret to their movement was under the page. He used levers that were connected to each other with tiny pins, or rivets, so that when you pulled one tab all the levers worked. This moved several parts of the drawing at the same time.

So many people liked Meggendorf's ideas that they began to copy them. And now movable and pop-up books are considered an art form. In fact, at the Cooper-Hewitt Museum in New York through Feb. 21 you can see a whole exhibit of these kinds of books.

But the best thing about pop-up and movable books is that you can think of them as miniature stages - where whole new worlds spread out between the pages.

The Equestrienne on the Platform In Mademoiselle Saltarella's number, the horse wears a little platform all strapped on; Mademoiselle Saltarella makes prodigious leaps while the horse gallops aroung the ring.

She lands on her feet. She is even capable of jumping through the hoop that a clown holds up for her. What a magnificent entertainment!