Quiet day.

Not a lot happened today, had an exciting walk to Tescos for dog food and then thought about going fishing but the weather looked a bit grim so didn't bother, lucky I didn't because it chucked it down later.
Now here is a question, many canal bridges in Birmingham have square apertures in their parapets (see below), what for? I have two theories;
1) They were put in when the bridge was built to enable horse manure, of which there would have been large quantities, to be shovelled directly into a boat below for transporting out to the farms for manure or,
2) They were cut during W.W.2 to allow fire pumps to lower their hoses directly into the canal for fire fighting during air raids.