How Four Discoveries Changed Lives

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.

Cyrus McCormick and the Reaper

An information text written for this worksheet. In the early 1800s, farmers cut ripe wheat by hand with a curved blade called a sickle or a scythe. Wheat must be harvested quickly once it is ripe, so a farm family could only plant as much as they could cut in a few weeks. In 1831, Cyrus McCormick showed a reaper on his family's farm in Virginia. Jo Anderson, a man enslaved on the farm, helped with the work, but the records say little about what he did. Pulled by a horse, the machine cut the wheat as it moved across the field. With a reaper, a few workers could harvest far more wheat in a day than many workers could by hand. In 1847 McCormick opened a factory in Chicago, close to the prairie farms. Farmers on the wide prairies of the Midwest began to plant much bigger fields, and fewer people were needed for farm work.