Despite the petroleum wealth of other lands, however, the United States far outdistances them, not only in the output of crude petroleum but in the manifold products extracted from it. The magnitude of the American industry may be gleaned from the fact that in the past year (1919) United States wells produced about 377,000,000 barrels, or over 65 per cent. of the world’s supply. The lead of Pennsylvania as the chief oil-producing state and the pivotal point of the world’s supply continued for many years, but has long since been superseded. For a number of years this state provided 98 per cent. of the oil production of this country. In 1891 the total production of Pennsylvania oil was 35,839,777 barrels, and in 1897 35,165,990 barrels, so that the maximum was reached in 1891. The greatest daily average production was during the month of November, 1891, when it reached 135,676 barrels. This pioneer territory suffered a gradual decline, and at the present time it is estimated that Pennsylvania produces about five per cent. of the American supply. Nevertheless, the output is considerably greater than in the boom days of the sixties when the phrase “Struck Ile” became an accepted synonym for the sudden acquirement of riches. As the importance of the industry grew, oil prospectors busied themselves in every part of the republic in probing for this source of wealth, and are still indefatigable after sixty years. What is known as the Mid-Continent fields, which includes such States as Kansas, Oklahoma and Wyoming, have developed enormous potentialities, while on the other side of the Rockies and the Sierras the California fields some years ago became one of the great sources of the world’s supply. The California development is an example of the rapidity with which an oil field can become productive on an enormous scale under modern methods. The records of achievement there show that it is possible, with the modern system of rotary drilling, to get down nearly 4,000 feet below the surface within the period of a month, depending on the nature of the formations, and the experience in that state demonstrated a finer quality of crude at such depths than could be produced from deposits nearer to the surface. California too furnishes at certain points an illustration of the mechanical ingenuity of the modern oil worker; for there are to be seen oil wells sunk in the sea at a considerable distance from the shore, the encroachment of sea-water being overcome by carrying the casing above high-water mark.