Mixed metaphors

A mixed metaphor attempts to create an extended comparison but fails because it is not consistent with itself. For example, in an essay on the language used in describing pain relief medicine, a student wrote:

"The topic of pain relievers seems clouded in a sea of medical terminology."

The metaphor is mixed because the images of cloud and sea do not match. The student should have said either "drowned in a sea of medical terminology" or "clouded in a fog of medical terminology." Metaphor can be effective, but only when the writer is fully aware of the images the metaphor accesses.