Quarter plate daguerreotype. (Occasional spotting, some tarnishing to perimeter). Housed in a Rare geometric union case [Berg 3-33] (chip to one corner). Littlefield, Parsons & Co. paper label behind image.

An outdoor image of the locomotive Mercury for the Boston & Worcester Railroad. A man stands between the cab and the open wagon car laden with wood fuel. The outer wheel frame is finely lettered "B.W. R. R." and "Mercury." Possibly a "builder's photo," made to show off the train. The Mercury was featured on the cover of the 1847 No. 1 issue of Bradbury & Guild's Rail-Road Charts: Boston to Albany.

The Boston & Worcester Railroad was chartered in 1831 and was opened for service to Worcester by July 1835 and quickly became the most important of the early Massachusetts rail lines as it formed the first leg of a route to Albany and the Hudson River valley, thus connecting Boston to the Erie Canal.

A 4-4-0 design, also known as the "American" type, the Mercury features four leading ("pilot") wheels followed by four drive wheels and no trailing wheels. This design allowed for larger fireboxes under the boilers and was the predominant style from the 1840s through the end of the 19th century.