[Webmagick-users] Lmost intelligent counters of the pendulum's vibration

[Lacy <sk...@av...>]

By a glass jar containing mercury. The rod he formed of steel of the
usual length; and because mercury expands five times more than steel, he
fixed the height of the column of mercury in the jar at only 6-1/2
inches. In this arrangement he found that additional heat carried up the
mercury in the jar, as much as it carried down the jar by the elongation
of the rod. Consequently, the motion of the one perfectly compensated
the motion of the other, and the effective centre of the weight always
remained at the same precise distance from the top of the rod. By the
application of this compensating pendulum, clocks are now constructed
that do not vary to the extent of a tenth of a second in a day. Soon
after the invention of Graham's mercurial pendulum, John Harrison--the
same clever mechanician who received L.20,000 from government for making
a chronometer that went to Jamaica in one year and returned in another
with an accumulated error of only 1 minute and 54 seconds--hit upon
another means of gaining the same end. He brought a steel rod down from
the point of suspension, turned it up into a copper rod of less length;
and from the top of this hung the weight. He fixed the lengths of the
steel and copper rods, which expand unequally, in such a way that the
steel carried the copp