Today's lecture is about the history of the bicycle. The earliest bicycles, called hobby-horses, appeared in the early 1800s and had no pedals. Riders pushed their feet along the ground to move. In the 1860s, pedals were added to the front wheel, but this design was unstable and difficult to ride. Then, in the 1880s, the safety bicycle was introduced, featuring two equal-sized wheels and a chain drive. This design made cycling much safer and more popular, especially among women, as it allowed them to wear regular clothing. By the early 1900s, bicycles had become a common mode of transport for many people.