This is my summary of the inventions I learned about in lessons one hundred one through one hundred four. In lesson one hundred one, I studied the invention of the air brakes. Before the air brakes were invented, it took trains a long time to come to a complete stop. The brake operators had to jump from car to car and turn the brakes on. This was a very dangerous job, and millions of operators were killed.

Westinghouse invented the air brakes after witnessing a terrible train crash. Two trains were on the same track, and they couldn’t stop in time. The air brakes could be activated on every car at once, and that certainly got rid of some of the time it took for trains to stop. But the air brakes were fail-proof, meaning even if the pipes containing the compressed air used to stop the train were fractured, the train would simply come to a complete stop.

In lesson one hundred two, I learned about the invention of the traffic light. In 1868, J. P. Knight solved London’s traffic problem with the invention of the traffic light. Knight was a train operator, and applied his knowledge from operating trains to invent the traffic signal. Traffic lights tell who has the right of way, and reduce the number of accidents caused by traffic.

In lesson one hundred three, I studied the invention of the tape measure. The modern tape measure was invented by Alvin J. Fellows in 1868. Fellows got inspiration from the British tape measure used for surveying, then added his own features to make it work for other things as well. The tape measure is made of a long strip of flexible metal rolled into a sort of spring, and can be accessed quickly.

Last of all, lesson one hundred four was about the invention of the pipe wrench. As oil and gas became more common pipelines were made to carry it from a well to train cars. However, the pipes were hard to work with, since the wrenches of the time were made for gripping square nuts and bolts. So, Daniel Stillson invented a solution in 1869 – the pipe wrench. The pipe wrench is a wrench that has small teeth cut into it so it can dig in and get a grip on iron pipes. To make it even easier to use, the pipe wrench works with a ratcheting system.