Mantle Clock

September 30, 2014 Posted by: David R. Daly
A cased clock with a mercury pendulum from the Beals Street parlor.
This glass encased clock is prominently displayed on the mantle in the parlor of the Kennedy family's Beals Street home.  It's gilded elements and bowed relief decoration recall an early 19th century French style, but it is actually a late 19th or early 20th century piece that only came to the attention of Mrs. Rose Kennedy at a much later date.

The clock's enamel face features Arabic numerals in a fancy Victorian script.  Like all other clocks in the house it reads three o'clock, the approximate time in the afternoon that John F. Kennedy was born in the upstairs master bedroom on May 29, 1917.  The decision to set all the clocks to three o'clock came directly from Rose Kennedy, who in an interview with the National Park Service stated of the future president's birth "he arrived at 3:00 in the afternoon."

One of the most interesting features of the clock is its pendulum, which has two cylinders filled with mercury to act as the weight, and can be adjusted to increase or decrease the speed at which it swings. Mercury pendulums, first invented by English clockmaker George Graham in 1721, were developed as a method of avoiding inaccuracies in earlier pendulum clocks caused by expansion and contraction of the pendulum rods due to changes in temperature. Mercury expands with an increase in temperature, and the mercury pendulum uses this property to counteract changes in other parts of the clock by shifting the pendulum's center of mass, thereby maintaining a more even rate of swing and resulting in more accurate timekeeping.

A receipt from 1967 indicates that the clock was purchased as part of Mrs. Kennedy's efforts to refurnish the house as a memorial and museum. Though it was bought in 1967 for $60 from the Jordan Marsh Company in Boston, the clock has a patent date of 1898 engraved upon it. A clock such as this one could have been present in the house when the Kennedys lived here.


Last updated: September 30, 2014

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