This is my summary of the inventions I learned about in lessons one hundred thirty-six through one hundred thirty-nine. In lesson one hundred thirty-six, I studied the invention of the diesel engine. The diesel engine was invented in 1893 by Rudolph Diesel. Diesel wanted to become an engineer from a young age, so he went to multiple engineering schools. He also learned about engineering from experience with building and fixing air conditioning systems for Carl von Linde. Diesel made many patents for Linde, but he wasn’t allowed to use them himself.

Because of this, Diesel began experimenting in areas Linde didn’t. He tried inventing a heat engine that ran on ammonia, but it exploded, and this nearly killed him. However, his experimenting eventually paid off, and he invented an engine that ran on a special fuel called ‘diesel’ in his honor. The diesel engine works using a high pressure instead of a spark plug to ignite the fuel, and this makes it more fuel-efficient than a gasoline engine. The parts all have to be able to stand higher pressure, so they’re also more likely to last.

In lesson one hundred thirty-seven, I learned about the invention of the mousetrap. Mice, rate, and other rodents carry lots of harmful bacteria, so people needed a good way to kill them. Mousetraps existed, but the most effective version we know today was invented by William C. Hooker in 1894. It consists of a spring-loaded bar that snaps down on a mouse’s neck when the mouse triggers a spring.

In lesson one hundred thirty-eight, I studied the invention of the radio. The radio was invented in 1895 by Guglielmo Marconi. Marconi invented the radio using Heinrich Hertz’s discovery of electromagnetic waves, and extended that to transmit sounds and videos over large distances wirelessly.

Last of all, lesson one hundred thirty-nine was about the invention of the semi-automatic shotgun. John Browning invented the semi-automatic shotgun in 1898. Browning was a gunsmith like his father, and he designed lots of different guns. The semi-automatic shotgun uses some of the firing power from one shot to load the next, though you have to load the first shot yourself. This makes shooting much quicker and easier, since you don’t have to stop to reload after every shot.