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ECON 3R03 Lecture Notes - Richard Trevithick, Barometer, Super Slow

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Jack Leach

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Steam Power Zahra Haidari
● Scientific knowledge does not automatically lead to invention
Turning a potentially good idea into a practical invention requires time, effort and money
There must be an economic incentive to justify bearing these costs
Extremely important breakthrough. Some people spent A LOT of money and hoped to get profit back.
Machinery is cheaper in England and therefore did not require much labour, reducing costs.
The Science
● Galileo discovered that a suction pump could not raise water more than about 9 meters
A suction pump creates a vacuum, partially fills the pump… and water gets pulled up.
A suction pump operates by creating a vacuum into which the water is drawn because, according to
Aristotle, “nature abhors a vacuum
The mystery was why the water stopped rising while a vacuum remained
Galileo was interested in this issue and confused as well, so he suggested the question to his
secretary, Evangelista Torricelli, and started working on an explanation.
● 1644: Torricelli inverted a tube full of mercury in a dish of mercury, and found that the column of
mercury stabilized at a height of 76 centimeters
His apparatus was essentially a barometer A barometer is still used for forecasting the weather.
He explained the result by arguing that the atmosphere had weight that pushed down on the mercury
in the bowl, supporting the column of mercury
1648: His hypothesis is confirmed by placing the barometer in a chamber from which the air is
pumped. The column falls as the air is pumped out, and rises when the air is readmitted
First steam operations operated from the force of the atmosphere.
● 1655: Otto van Guericke places two hemispheres together and pumps out the air. It takes 16 horses to
separate them. Anything less than 15 horses would not. The atmosphere is pressing to hemispheres
together and it’s extremely difficult to pull them apart. It takes work to undo the effect of the
● 1672: van Guericke uses a piston and cylinder to perform work. When air is pumped out of the
cylinder, atmospheric pressure pushes the piston down, lifting a weight attached to the piston
● 1675: Dennis Papin creates a vacuum in a cylinder by filling it with steam, and then condensing the
● 1698: Thomas Savery makes first use of steam power
in a pump, not in an engine
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