Java, Sumatra, Borneo, and possibly the Philippines are capable of adding to the supply, and there are further deposits in Peru and elsewhere in South America. It should be born in mind, by the way, that oil prospecting is not so simple as is the search for other minerals. It is noticeable that oil, thus far, has been found principally near well-populated districts, leaving less accessible territory for future prospecting, when the present supply may threaten to decline. Already Alaska is being studied. Oil prospects near Cook's Inlet on the Copper River, for example, are attracting considerable attention.
Petroleum occurs most irregularly, both geographically and geologically.
It is found here and there in th old world as well as the new. There is no geological period characteristic of it. We find it in Tertiary sand and gravel in Russia and in California and in rocks as old as the lower Silurian in Ohio and Indiana. This gives additional interest to the speculation as to where it comes from, the disputes on which subject have been as varied as the speculations have been vague. In California, in Texas, and elsewhere in this and other countries, prospecting goes on, and oil wells are being rapidly developed.