This is my summary of the inventions I learned about in lessons sixty-one through sixty-four. In lesson sixty-one, I learned about the invention of the jackhammer. In 1848, a steady stream of inventions based on the steam engine led to Jonathan Couch’s invention of the jackhammer. The jackhammer uses steam to power a piston with a drill attached, and can break through hard surfaces. Steam powered jackhammers were later replaced by jackhammers powered by compressed air for safety reasons.

In lesson sixty-two, I studied the invention of the pin-tumbler lock. Linus Yale invented the pin-tumbler lock in 1842 for the banking industry. Pin-tumbler locks are difficult to pick, but easy to rekey. The lock relies on a series of pins, each made up of two parts. The key has a pattern of peaks and valleys that push the pins until they line up, allowing the lock to turn freely.

In lesson sixty-three, I learned about the invention of the safety pin. Walter Hunt was an inventor, and invented the safety pin so he could patent it, sell the patent, and use the money from it to pay off his debt. However, the safety pin became much more popular than he counted on. The big benefit of the the safety pin is pretty obvious: it keeps the end of the pin from sticking into you.

Last of all, lesson sixty-four was about the invention of the gyroscope. Leon Foucault invented the gyroscope in 1852 as a smaller, simplified experiment to demonstrate the earth’s rotation. Gyroscopes are spinning discs positioned in gimbals that provide stability. They can be used in aircraft to maintain direction.