Or maybe this was not used for a fire alarm circuit (as a lot of them were), thus for some other purpose of stringing a pair of wires. At any rate, this is a cool shot of one of these rarely seen heavy-metal entities that most insulator collector go-with enthusiasts would drool over. Also noted is some old overhead wiring for the trolleys at the time. Very similar construction still is in use servicing the street cars that are around and about in Boston and Cambridge, MA.