These four cases were argued together. They are based on the same original transaction. That is a written lease dated May 7, 1881. It expressly declares the property “shall be occupied and worked for petroleum, rock, or carbon oil, and shall not be occupied or used for any other purpose whatsoever.” And “if no oil is found in paying quantities within four years from this date, this lease shall be null and void.”

Oil was not so found. It would be a clear perversion of language to hold that gas and oil are synonymous terms. The evidence is insufficient to prove that the word “gas” was omitted from the lease through fraud, accident, or mistake. The doctrine of equitable estoppel is not applicable to the facts proved.

There is no error in the judgments nor in the decrees; therefore, judgments and decrees are severally affirmed and the appeals are dismissed, at the costs of the respective appellants.