For the same reason, however agreeable at first long allegories may be by their novelty, they never afford any lasting pleasure: witness the Fairy Queen, which with great power of expression, variety of images, and melody of versification, is scarce ever read a second time.
In the fourth place, the comparison carried on in a simile, being in a metaphor sunk, and the principal subject being imagined that very thing which it only resembles, an opportunity is furnished to describe it in terms taken strictly or literally with respect to its imagined nature. This suggests another rule, That in constructing a metaphor, the writer ought to confine himself to the simplest expressions, and make use of such words only as are applicable literally to the imagined nature of his subject. Figurative words ought carefully to be avoided; for such complicated images, instead of setting the principal subject in a strong light, involve it in a cloud; and it is well if the reader, without rejecting by the lump, endeavour patiently to gather the plain meaning, regardless of the figures:
A stubborn and unconquerable flame
Creeps in his veins, and drinks the streams of life.
Lady Jane Gray, act 1. sc. 1.
Copied from Ovid,
Sorbent avidæ præcordia flammæ.
Metamorphoses, lib. ix. 172.
Let us analize this expression. That a fever may be imagined a flame, I admit; though more than one step is necessary to come at the resemblance. A fever, by heating the body, resembles fire; and it is no stretch to imagine a fever to be a fire.
Again, by a figure of speech, flame may be put for fire, because they are commonly conjoined; and therefore a fever may also be imagined a flame. But now admitting a fever to be a flame, its effects ought to be explained in words that agree literally to a flame. This rule is not observed here; for a flame drinks figuratively only, not properly.
King Henry to his son Prince Henry:
Thou hid’st a thousand daggers in thy thoughts,
Which thou hast whetted on thy stony heart
To stab at half an hour of my frail life.
Second Part Henry IV. act 4. sc. 11.
Such faulty metaphors are pleasantly ridiculed in the Rehearsal: