In the interests of accuracy and practical convenience, a detailed account is given of several instances well known to the author where vague or badly chosen place-names have given rise to uncertainty or even definite errors, in the position of geological localities, including one recent description of an important deep boring in N.E. Yorkshire. Attention is also drawn to an increasing looseness in the definition of the ancient local name of Cleveland. Trouble has also been caused by the recent invention of a new place-name, Ravenscar, which is synonymous with the ancient name, Peak (not The Peak, as often written by geologists). When an author is not himself thoroughly conversant with the place-names of his district it is recommended that some local authority, not necessarily a geologist, should be consulted.