What is that horse pulling?

We recently came across this picture in our archives.  It was definitely not taken in Acton.  We have no idea who took the picture, where or when it was taken, or why it is in our collection.  The picture is unlabeled. 

What is the horse pulling?  Our guess is that it was a street-sweeping apparatus.  It is hard to see, but there may be brushes underneath, behind the wheel.  Can anyone confirm that?  Has anyone seen a rig like this?  Please contact us if you have any information that would help to identify the machine or the time and/or place in which the picture was taken.