（解説文要約）
石炭を積み込んだ炭車は、巻揚機で引き揚げられます。

この作品には、画面右のチェーンと画面左のドロバーを使用した連結の方法を時代別に描いています。

たっぷりと石炭が積み込まれた炭車が連結されるとかなりの重量。

チェーンやドロバーが破損し、炭車が逆走すると大きな事故となることもありました。

 

 

 

Coal cars filled with coal are connected to a winch and carried out of the pit.
This painting describes methods of connecting chains, illustrated on the left side; and draw bars, illustrated on the right side of the picture, over time.
Chains come from the winch, and draw bars are attached to the coal cars.

So, when connected, the illustrated methods were used.
If any breakage of a chain or a draw bar occurred, coal car would run down backwards leading to serious accidents.
Fully loaded cars were quite heavy when connected.