Who invented it? Nicholas-Jacques Conte. When was it invented? 1795. Where was it invented? Nuremburg, Germany. How does is work? Graphite molecules are flat groups of carbon atoms that are stacked in layers. The layers slide against each other and allow the lead to slide off the pencil point and onto the paper. When you erase with a rubber eraser, the graphite in the lead sticks to the rubber better than it does to the paper. Why is it important? So that people can write and if they make a mistake, they can erase it.
Who invented it? René Laennec. When was it invented? 1816. Where was it invented? France. How does it work? The disc and the tube of the stethoscope amplifysmall sounds such as the sound of apatient’s lungs, heart, and other sounds inside the body, making them sound louder. The amplified sounds travel up the stethoscope’s tube to the earpieces that the doctor listens through. Why is it important? So that doctors can hear people’s heartbeat to see if there are any problems with it.
Who invented it? James Henry Greathead. When was it invented? 1825. Where was it invented? England. How does it work? Behind the diaphragm an erector arm, an adjunct of the shield, constructs the tunnel lining by successively setting segments of steel rings in place. The steel is later covered over with masonry. Hydraulic jacks to advance the shield are braced against the end of the completed lining. Why is it important? So that there aren’t cave ins and that people don’t die to cave in’s.
Who invented it? John Loudon McAdam. When was it invented? The 18th century. Where was it invented? Scotland. How does it work? Using a combination of manual labor and planning machinery, called graders, the surface layer is smoothed and leveled. Aggregating: Once the soil has been leveled, an aggregate base of soil, concrete and limestone is used to stabilize the roadway. During this phase, curbs, gutters, and drains are also constructed. Why is it important? So that people can drive cars on it smoother than on a brick road.