“How do locomotives hear?”/“Through the engineers.”

A classic train riddle is:
   
Q: How do locomotives hear?
A: Through their engine ears (engineers).
 
The riddle was printed in the Waterloo City (IN) Press, “Queer Queries” by Prof. G. Howe Green, on February 4, 1869.
 
           
Newspapers.com
4 February 1869, Waterloo City (IN) Press, “Queer Queries” by Prof. G. Howe Green, pg. 4, col. 1:
How do locomotives hear?–Through their engine ears (engineers.) 
 
4 January 1870, Daily Eastern Argus (Portland, ME), pg. 1, col. 8:
How do locomotives hear?–Through their engineers.
 
Google Books
25 June 1870, Harper’s Bazar, pg. 416, col. 4:
How do locomotives hear?–Through their engineers.
 
Google Books
The Handbook of Conundrums
By Edith Bertha Ordway
New York, NY: Sully and Kleinteich
1915
Pg. 126
How do locomotives hear? Through their engin-eers.
       
Google Books
Just Jokes a Collection of Kids Jokes
By Phyllis Agles-Johnson
Lulu Press (Lulu.com)
2010
Pg. 18:
Q. How do locomotives hear?
A. Through the engineers
 
Twitter
Pearl Lane-Soliz
@PearlLaneSoliz
[Joke Time] How do locomotives hear? ... Through the engineers. #jokes #funny
5:35 PM · Apr 8, 2010·Twitter Web Client
   
Google Books
Riddles, Riddles, Riddles:
Enigmas and Anagrams, Puns and Puzzles, Quizzes and Conundrums!
By Joseph Leeming
Mineola, NY: Dover Publications
2014
Pg. 160:
How do locomotives hear?
Through their engineers (engine-ears).
 
Reddit—Dadjokes
Posted by u/MyJelloJiggles May 10, 2020
How do locomotives hear?
Through the engineers.