I believe it was the first funnel. Didn't they find damage on the starboard bridge wing and concluded that it was likely caused by the falling funnel which crushed the starboard bridge wing?
Colonel Gracie:
"The forward funnel broke from the ship, falling on the starboard side into the sea."
Harry Senior:
"Before I dived off the ship one of the forward boilers burst and blew up the forward funnel."
Charles Lightoller
"The terrific strain of bringing the after end of that huge hull clear out of the water caused the expansion joint abaft
number 1 funnel to open up. The fact that the two wire stays to
this funnel on the after part led over and abaft the expansion joint, threw on them an extraordinary strain, eventually carrying away the port wire guy, to be followed almost immediately by the starboard one. Instantly the port one parted, the funnel started to fall, but the fact that the starboard one held a moment or two longer, gave this huge structure a pull over to that side of the ship."
John Poingdestre
Q - Now will you describe to us what you saw happen when she sank?
A - Well, I thought when I looked that the ship broke at the foremost funnel.
Q - What led you to that conclusion?
A - Because I had seen that part disappear.
Q - If she sank by the head you would see that part disappear, would you not?
A - Yes.
Q - What was there about the disappearance that led you to think she broke?
A - Because she was short; the afterpart righted itself after the foremost part had disappeared.
Edward Brown also witnessed the ship break. When asked where he was at the time, he said he was, "In the water, right before the forward funnel."
The above accounts are similar to Thomas Dillon's account in this British newspaper when he possibly had witnessed the forward expansion joint opening up.
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