Without context clues, people won't know who "they" are. Are they his friends? Cousins? Strangers? So, the sentence would stay the same as it is. (With a few fixed grammatical mistakes)
The three purposes of writing are to Persuade, Inform, and Entertain. To remember this think of P.I.E. By the process of elimination, you know the author is Informing you about the Industrial Revolution.
