Retractile drawbridge

A retractile drawbridge is a rare type of moveable bridge in which the span is pulled away diagonally on rails. It is a variant of the retractable bridge. Only four examples are known to exist in the United States.^[1] It is believed to have been invented by T. Willis Pratt in the 1860s.

^ Record, Historic American Engineering. "Summer Street Retractile Bridge, Spanning Fort Point Channel at Summer Street, Boston, Suffolk County, MA". www.loc.gov. Retrieved 2019-03-26.

[1] Record, Historic American Engineering. "Summer Street Retractile Bridge, Spanning Fort Point Channel at Summer Street, Boston, Suffolk County, MA". www.loc.gov. Retrieved 2019-03-26.

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