Probably the most commonly cited theory of the explosion of the Sultana is a combination of low water and careening of the boiler.
According to this theory, the water level was low and as the boat rocked, or careened, the boiler iron was exposed to the heat of the fires without water covering and cooling it. The iron turned red hot and when the boat rocked back, the water striking the metal flashed to steam creating a sudden pressure surge and subsequent explosion.
The emphasis and acceptance of this explosion theory is due to the large amount of testimony that discusses careening and low water. In testimony or affidavit, Isaac West (Boilermaker and Engineer), WB Richardson (Chief Engineer of the steamboat Marble City), JJ Witzig (supervising inspector of steamboats, St. Louis), RG Taylor (boilermaker) and Sultana Chief Engineer Nathan Wintringer all noted that careening of the boiler may have been the cause of the explosion. Four of these individuals were not on the boat and the fifth, Chief Engineer Wintringer, was asleep at the time of the accident.
Union Captain Frederic Speed was court-martialed for his role in the overloading of the boat. The prosecution at his trial asked multiple questions regarding careening of the boat. Due to the large number of troops on board and the small amount of cargo in the hold, the boat did rock to one side when many men rushed there, notably during the last picture (above) taken of the Sultana in Helena, Arkansas.
Calm before the storm
At the time of the explosion, the men were mostly asleep and not moving side to side as mentioned in the careening theory. There was no mention in any of the survivors’ stories of a rocking boat before the explosion. In a letter to the Secretary of War, dated May 19, 1865, General Hoffman, one of the Army investigators, noted that, “There is nothing to show that there was any careening of the boat at the time of the disaster, or that she was running fast; on the contrary, it is shown that she was running evenly and not fast.”
The testimony of the experts stated that it was likely careening and low water in the boilers that caused the explosion, and this was accepted as fact. We now know that they did not understand how or why boiler explosions were so powerful nor why they most commonly occurred. Soldier recollections and other testimony indicate that the boat was not rocking.
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