Final answer:
The excerpt does not detail how George Stephenson's genius transformed steam engines for the transport of passengers and goods, which is the information not explained in "The Steam Engine".
Step-by-step explanation:
The excerpt explains the significant breakthroughs and the evolution of steam engines and their contribution to the transportation revolution, primarily focusing on the innovations that occurred in Britain. It does not specifically state that George Stephenson's genius transformed steam engines to transport passengers and goods, an achievement attributed to him in other sources. Thus, the answer to what is explained in this excerpt that is not explained in "The Steam Engine" is C. George Stephenson's genius transformed steam engines to transport passengers and goods.