1890 house wiring issues. Help!
So I've been doing a renovation on an 1890 house for the past several years, but I haven't done anything to the electrical in the house for at least the last year.
The problem is that suddenly, last weekend, the breaker for the circuit that powers all the lights on the first floor started tripping. Nothing was done to provoke this reaction (no new wiring/extra appliances added to the circuit/etc.). I called an electrician and he used an ammeter to determine that the circuit was pulling 60 amps for the short time that it would stay on.
Oh, and I should mention that it wasn't tripping immediately. It would go on and produce an audible humming inside the breaker panel and then trip after 5 to 10 seconds.
The electrician was unable to remedy the problem, but he was able to isolate the offending leg of the circuit by disconnecting it at a junction just inside the house from the breaker panel. So I have a few lights on the first floor, but the majority of the lights are still not operational.
So basically the mystery is: sudden onset of breaker tripping, circuit pulling 60 amps for no known reason, circuit seems to need to "charge up" to the point of tripping the breaker (ruling out a direct short somewhere in the line).
I am at a loss on this one and apparently so was the electrician I called. I have accepted that I may need to pigtail off of other circuits in the rooms with the non-working lights, but I thought I would take a stab and see if anyone here has encountered a similar problem.
Please help if you can.