How Four Discoveries Changed Lives
D2.His.14.3-5
Read each information text, then answer the questions.
Louis Daguerre and the First Photographs
An information text written for this worksheet. Before 1839, the only way to keep a picture of a person or a place was to draw or paint it, which took a skilled artist many hours. Louis Daguerre, a French artist, worked for years on a way to fix an image made by light onto a metal plate. In 1839 the French government announced his method, called the daguerreotype, and soon made it free for people to use. Within a few years, photography studios opened in cities in Europe and the United States. For the first time, ordinary families could have pictures of themselves. Historians and newspaper artists could now work from real pictures of faces and places from events, not only drawings.
- 1. Why did ordinary families rarely have pictures of themselves before 1839?
- 2. What was Daguerre's method called?
- 3. Why could photography studios open in many cities within a few years?
Louis Pasteur and Safer Milk
An information text written for this worksheet. In the 1800s, milk and other foods often spoiled quickly, and milk could carry germs that made people, especially young children, very sick. Louis Pasteur, a French scientist, showed in the 1860s that tiny living things called microbes make food spoil. He found that heating a liquid such as wine for a short time, without boiling it, and then cooling it, killed most of the harmful microbes without ruining the taste. This method is named pasteurization, after him. Later, cities in Europe and the United States began to require that milk be pasteurized. Fewer children became sick from milk, and milk stayed fresh for longer, so it could be shipped farther.
- 1. Why could pasteurized milk be shipped farther?
- 2. What did Pasteur show makes food spoil?
- 3. Why did it matter that the method did not ruin the taste?
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