Why is the living room floor of Zeng Guofan's former residence earthen?

The floor of Zeng Guofan's front living room is the original appearance of the earth.

One of the four famous ministers in the late Qing Dynasty, the Han nationality, whose first name was Zicheng, whose real name was Bo Han and whose real name was Sheng Di, was the grandson of the 70th Saint Ceng Zi, a modern politician, strategist, philosopher and writer in China, and the founder and commander-in-chief of Xiang Army.

Bai Yutang, the birthplace of Zeng Guofan and the first former residence, is located at the foot of Gaoling Mountain in Tianping Village, Ye He Town, kilometers away from Fushoutang. In the 16th year of Jiaqing, 1 81year,1year, Zeng Guofan was born here.