Boswell and Johnson held a conversation upon this experiment as
follows:--_Boswell._ "Why, sir, do people play this trick, which I
observe now when I look at your grate, putting the shovel against it to
make the fire burn?"--_Johnson._ "They play the trick, but it does not
make the fire burn. _There_ is a better (setting the poker
perpendicularly up at right angles with the grate.) In days of
superstition, they thought, as it made a cross with the bars, it would
drive away the witch."
Upon this, Dr. Kearney notes: "it certainly does make the fire burn: by
repelling the air, it throws a blast upon the fire, and so performs the
parts, in some degree, of a blower or bellows." These observations were
made only as to the shovel, but the poker is equally efficacious. "After
all," says Croker, "it is possible that there may be some magnetic or
electrical influence, which, in the progress of science, may be
explained; and what has been thought a vulgar trick, may be proved to be
a philosophical experiment."
Whatever may be the cause, there is every-day evidence that a poker or
shovel, as the case may be, if laid across a dull fire, will revive it;
because, we think, the poker or shovel receives and concentrates the
heat, and produces an additional draught through the fire.
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