This is my summary of the inventions I learned about in lessons eighty-one through eighty-four. In lesson eighty-one, I studied the invention of the ironing board. The ironing board was invented in 1858 as ironing became more common in homes. Ironing is important because wrinkle-free clothing makes a good impression. The ironing board has two sides: a wide, flat side used for ironing most things, and a narrow side used for ironing tougher parts such as arms and legs.

In lesson eighty-two, I learned about the invention of the internal combustion engine. Before the internal combustion engine, steam engines were widely used, but they took too long to start and stop. However, Etienne Lenoir changed this in 1859.

Etienne Lenoir was fascinated with electricity, especially how sparks can ignite combustable gasses. He discovered that a combination of oxygen and gasoline can be ignited with a spark, and he built the internal combustion engine off that concept. The internal combustion engine has pistons, just like a steam engine, but is powered by small explosions instead of steam or a vacuum.

The internal combustion engine is smaller than a steam engine, and produces more power to turn a drive shaft through a four-stroke process. The drive shaft can then be used to turn things such as wheels of a car or a propeller. The internal combustion engine doesn’t rely on steam- which has to heat up- so it can be turned on instantly.

In lesson eighty-three, I studied the invention of the lever-action repeating rifle. The musket rifle was used by most soldiers, but it was slow to load. Benjamin Tyler Henry was a gunsmith, and he invented the repeating rifle in 1860 as an alternative. The repeating rifle could fire sixteen rounds in quick succession, and was quick and easy to lead compared to the musket.

Last of all, lesson eighty-four was about the invention of the twist drill. Steven Morse invented the twist drill bit in 1861. The twist but cuts a clean hole, and it lifts debris out of the hole it makes as it turns due to the grooves cut in it.