BOSTON (AP) — A modern-day metallurgical engineer is shedding new light on one of the more bizarre yet most tragic episodes in the history of Boston.

In January 1919, a giant storage tank in the city's North End ruptured, sending 2.3 million gallons of molasses pouring down city streets, killing 21 people.

Ronald Mayville, a senior structural and metallurgical engineer with Simpson, Gumpertz & Heger in Waltham, has researched the disaster for years in his spare time.

He tells The Boston Globe (http://bit.ly/1wZdmKQ ) the walls of the tank were at least 50 percent too thin and the type of steel used was brittle because it contained a low amount of the chemical element manganese, making it more likely to crack.

His research was featured in the September edition of Civil and Structural Engineer Magazine.

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Information from: The Boston Globe, http://www.bostonglobe.com