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After graduating from high school in Hartford, Wu studied mining and metallurgy at Columbia University in New York. He returned to Kailuan to work at the coal mine in 1881, then went to London to study mining again in 1890. Later he explored coal mines in many places of China.

Speaking of his great-grandfather at the gathering last month, Wu Shouhao says he never knew that history until 1998.

"Due to the political environment, especially the 'cultural revolution' (1966-76), my family kept it as a secret," says Wu, former general manager for Pepsi in China.

"But once I knew the history, I felt so proud for my great-grandfather and his blood in my veins."

Tang Shaoming is the grandnephew of Tang Guo'an, one of the Hartford students, who later became the first chancellor of Tsinghua University. He says the mission 140 years ago had profound meaning.

"China recognized itself as the Middle Kingdom of the world for hundreds of years. We were teachers, but this mission marked that the country realized the world order had changed."

The students, he says, "were too young to understand the heavy responsibility on them, but I believe that they had seen how the country had suffered from invasion, chaos and poverty".

The Chinese students witnessed a great era of inventions: They were in the US when Thomas Edison recorded and reproduced sounds on the phonograph. Alexander Graham Bell developed the first telephone at the time.