The narrator is a former soldier, working as civilian bossing coolies working on a railroad. He is told some
soldiers up the line are planning to cause trouble. So
he goes up there to head off trouble. In his Irish speech,
I think "throlly" = trolley = hand car, a small rail maintainance car, propelled by a see-saw with handles to
drive a gear. In US called a gandy dancer.


Source: The Collins English Dictionary © 2000 HarperCollins Publishers:

gandy dancer ['gændý]
noun (slang)
a railway track maintenance worker
[ETYMOLOGY: 20th Century: of uncertain origin]

Here's a URL to some pictures of an old railroad set up on
a big fruit farm to entertain customers and tourists. There are a number of pictures. The one labelled "Proud William"
is of a small car for maintaince, but I don't see the handles that propelled it.
http://www.phoenixandholly.com/pages/proud_william_jpg.htm

Here's another URL with a lot of information, but sadly I didn't find any pictures. But if you are really interested,
I think there are links where you may find them.
http://www.pressrepublican.com/Archive/2003/06_2003/06292003gl.htm