Zhang Heng

Zhang Heng is a man who served during the reign of Emperors ­­­­Andi and Shundi [Eastern Han Dynasty] as an astronomer, engineer, mathematician and painter. He comes from a long line of astronomers who served the emperors throughout multiple dynasties. (Shea, 2007) His engineering achievements include the estimation of pi as the root of 10, a powered armillary sphere and a seismometer. His contributions helped not only the people of his time; his mathematical knowledge and engineering breakthroughs also helped China as a country advance in their mechanical engineering even after he passed away.
Armillary Sphere
The Armillary Sphere is a celestial globe used to track the stars. In Ancient China, it was used to aid “calendrical computations and calculations”. (Wikipedia, 2015) It was first created by Geng Shoucang at around 70BC to 50BC. Zhang Heng later created a bronze model of this, and further improved on it by remapping over 2000 stars, along with powering it to make it rotate fully once a year. To power it, he implemented a complex gear system which was linked to the armillary sphere to a water clock. A water clock works in a method such as water dripped from one pan to another the weight of the pans would drive the gears to slowly move, thus making the sphere advance. He also added a gear-driven device which demonstrated the movements of the moon. (Shea, 2007) This allowed for more accurate calculations for their calendars and greater advances in mechanical engineering in China in later years.
Seismometer
A seismometer is a device which measures the motion of the ground, including seismic waves created by earthquakes, volcanic eruptions & rockslides. The first ever seismometer was created by Zhang Heng, and was used to show the direction of where an earthquake happened, so the state can provide help as soon as possible where the earthquake was. This is supported by a book known as Book of Later Han which records that on one occasion, Zhang's device was triggered, though no observer of the device had felt any seismic disturbance; several days later a messenger arrived from the west and reported that an earthquake had occurred in Longxi, the same direction that Zhang's device had shown, and thus the court was forced to admit the effectiveness of the device. (Wikipedia, 2015) The way this seismometer worked was unknown until fairly recently, when a group reconstructed the seismometer, allowing an insight as to how it worked.
The seismometer has eight tubed projections, shaped like dragon heads. A bronze ball falls to its corresponding metal object underneath it, shaped like toads with their mouths gaping open, each representing one direction: North, South, East, West, Northeast, Northwest, Southeast and Southwest. The device had eight mobile arms connected with cranks which have catch mechanisms at the periphery. When they are tripped, a crank and a right angled lever which would raise the head of the dragon, dropping the ball which was supported by the lower jaw into the toad’s mouth. This showed the direction of which the earthquake happened, and aided the state in aiding those affected by said earthquake, although it could not predict earthquakes.
James Watt

James Watt was an Industrial Revolution engineer whose improvements on the Newcomen Steam Engine incited the Industrial Revolution throughout the world. (Wikipedia, 2015) This steam engine was known as the Watt Steam Engine, alternatively known as Boulton and Watt Steam Engine. This Steam Engine yielded higher efficiency when compared to the Newcomen Steam Engine. The first improvements were on the broiler, which allowed him to measure the amount of water and steam. He then created separate condensers, further increasing the efficiency of engine. Other inventions of his include: the coining of the term ‘Horsepower’, Flexible water mains, Letter-copying press, a machine for copying sculptures, a micrometer (now known as a rangefinder) and a