The skin on the ends of our fingers has ridges on it. These ridges show clearly through a magnifying glass. About 120 years ago an Englishman made an amazing discovery. He found out that no two people have exactly the same pattern of ridges on their fingertips. The Eng­lishman was Sir Francis Galton.
   The British government saw a way of putting this discovery to use. They began using fingerprints to track down criminals. A fingerprint is merely a record of the pattern of ridges on a person's finger. It is easy to make a fingerprint. All one has to do is to press his finger on an inked pad and then on paper. The English police started a file of the fingerprints of all the criminals they caught. Later, if finger­prints were found at the scene of a crime, the police could check with their finger­print files. In many cases they found that the crime was committed by someone whose fingerprints were on record.
   Now every police department has its fin­gerprint file. It is a big help in catching criminals. But fingerprints are useful in many other ways, too. Many hospitals fin­gerprint newborn babies. Then the babies cannot get mixed up. Soldiers are finger-printed. Their fingerprints help identify them if they are killed or badly wounded. Government workers are fingerprinted as a way of helping guard important secrets.