This is my summary of the invention I learned about in lessons one hundred twenty-one through one hundred twenty-four. In lesson one hundred twenty-one, I studied the invention of the light bulb. Before the light bulb was invented, there was the arc lamp. The arc lamp was very bright, but it took too much power to use on a regular basis.

In the end, Thomas Edison came up with a solution in 1879: the light bulb. However, it wasn’t easy – Edison went through over 3,000 versions of the bulb, and 6,000 plant-based filaments before he came across just the right combination! The light bulb consists of a glass bulb with a wire inside called a filament. When an electrical current passes through the filament, it heats up. When it heats up enough, the light bulb produces a hot, bright, white light.
In lesson one hundred twenty-two, I learned about the invention of the cash register. The cash register was invented by James Ritty in 1879. Ritty owned a saloon, but he had a problem: like most store owners, Ritty’s employees were stealing from him. They’d slip a bit of cash out of the cash drawer when he wasn’t looking, and it irritated him. Then, while on a ship to Europe, Ritty noticed a machine that counted every time the propeller made a full revolution; this inspired him to apply it to his business, and he invented the cash register.

The cash register ring a bell every time a transaction is entered into it. It also makes it much harder to steal from the cash drawer, since it only opens if the cash register calculates that change is needed. Ritty wasn’t successful in selling his cash register – he probably should have used better advertising. He was overwhelmed by running two businesses, though, so he sold his patent to what would later become the NCR (National Cash Register Company). They had much better success, since they could focus more on selling cash registers. They appealed to shop owners who wanted a solution for their stealing-employee problem, and sold millions of cash registers that way.

In lesson one hundred twenty-three, I studied the invention of the thermostat. Warren Johnson invented the thermostat in 1883. He worked in the University of Wisconsin as a science professor. Johnson’s thermostat used a bimetallic strip that would cause a bell to ring, which told the heat operator to turn on or off the heat.

Last of all, lesson one hundred twenty-four was about the invention of the steam turbine. Before the steam turbine was invented, electric generators (also called dynamos) were powered by steam engines. This was pretty inefficient, though, so another method was needed. This came in the form of the steam turbine.

The steam turbine was invented in 1884 by Charles Parsons. Parsons was inspired by another steam turbine that was invented around the same time, but had some major faults. One of these was that the metal the turbines were constructed out of couldn’t stand the high temperature of the steam, so Parsons used another material. When the steam comes out of the power pant and hits the turbine, the turbine turns. The turbine is connected to a shaft, which powers an electric generator.