A figure of speech is an expression that uses words imaginatively (rather than literally) to make abstract ideas concrete. Most often, figures of speech compare two seemingly unlike things to reveal surprising similarities.

In a simile, the writer makes the comparison explicitly, usually by introducing it with like or as: By the time cotton had to be picked, Grandfather’s neck was as red as the clay he plowed. In a metaphor, the like or as is omitted, and the comparison is implied. For example, in the Old Testament Song of Solomon, a young woman compares the man she loves to a fruit tree: With great delight I sat in his shadow, and his fruit was sweet to my taste.

Although figures of speech are useful devices, writers sometimes use them without thinking through the images they evoke. The result is sometimes a mixed metaphor, the combination of two or more images that don’t make sense together.

Flew suggests an airplane, whereas under a full head of steam suggests a steamboat or a train. To clarify the image, the writer should stick with one comparison or the other.

Here the writer is mixing airplanes and stoves. Simply deleting one of the images corrects the problem.