the alcohol radicals, the consecutive members of which were isomeric and differed in their boiling points by 30° C. There were also found the more volatile members of the ethylene series, and in the Rangoon petroleum some of the members of the benzole series. Very little is known concerning the denser constituents, whose boiling points are above 200° C. Some petroleums contain more than one per cent. of nitrogen, others contain sulphur. The amount of carbon increases with the density, and that of hydrogen decreases.—The process of sinking the wells is described in the article Artesian Wells. The productive wells vary greatly in depth. In some large supplies have been afforded at 60 or 70 ft., and in others at greater depths to over 1,000 ft. Most of the oil is from wells over 180 ft. deep. Shallow wells, that are exhausted by pumping, are successively made to yield again by sinking them deeper. The oil is found at several zones or oil-producing belts at different depths. Several wells may continue in successful operation near together without seeming to draw upon each other; and again wells may be sunk near others that are producing largely, or near the natural springs of oil, and prove unsuccessful. The pumps are sunk deeper into the wells as the supply goes down; and it is observed that if the pumping is interrupted for a day, the product obtained when it is renewed will be water, which is more or less salt. At some wells the flow of water has continued during several days' pumping before the oil was recovered. This never seems to fail entirely, unless it be from some obstruction arresting the flow, and then recourse is had to sinking deeper or enlarging the bore of the hole. Salt water commonly comes up with the oil, and is separated from it by standing in the vats into which the products are received. The proportion of this to the oil is very variable, and the quantity of oil daily pumped from a single well is far from being regular. Sometimes the oil, when first struck, rushes up with great violence by reason of the pressure of the carburetted hydrogen gas that accompanies it. This produces a spouting or flowing well, from some of which the yield has been more than 1,000 barrels a day for a long time; but the quantity gradually diminishes until they cease to be flowing wells, and they are then pumped. In a few instances the oil has leaped forth with such violence as to be beyond control, and immense quantities have been lost. These fountains of oil have sometimes taken fire, producing terrific conflagrations and presenting scenes of appalling grandeur.—Petroleum acquired a reputation as a medicine before it was used for other purposes; and there is no doubt it possesses some virtue, especially as an outward application in diseases of the skin, chilblains, rheumatism, &c. Taken internally in doses of 30 to 60 drops, it acts as a sudorific and stimulating anti-spasmodic. It has been recommended for disorders of the chest, and in Germany as a remedy for tapeworm. Its use for illuminating purposes has become of vast importance; and it is becoming each year of more extended application in technology, the waste products of its manufacture yielding a great variety of useful products. (See Petroleum Products.) Very large quantities are used raw or unrefined; but the purposes to which it is applied are few, and the consumption is almost exclusively confined to the denser varieties, such as are found in Ohio and West Virginia. It is used chiefly as a lubricator, for fuel, and in the manufacture of gas. As a lubricator for heavy journals, either pure or mixed with tallow or animal oils, it is of great value, especially for the axles of railroad cars, in rolling mills, &c. For fuel it has been made the subject of many elaborate experiments and voluminous reports from the government engineers of this and other countries, many of which have been highly favorable. Several furnaces have been contrived for its combustion for steam and other purposes, yet it has been but little used as fuel. The reason for this apparent neglect of such an abundant, cheap, and efficient source of artificial heat is no doubt thus far to be attributed to its comparatively dangerous properties and to other difficulties attending its transportation and storage. These difficulties and the prejudices attending them are gradually disappearing, and we seem to be rapidly approaching a time when the consumption of crude petroleum, especially for steam purposes, will become enormous. It has been used to a limited extent for the manufacture of illuminating gas. For this purpose it is allowed to drip on to coke heated red hot in a retort, and the gaseous products conducted to a gasometer.—The table below will give the reader some idea of the vast amount of this material which has been yielded by the Pennsylvania oil region alone, from 1860 to 1873 inclusive:
| YEARS. | Bbls. of 40 gallons. |
| 1860 | 500,000 |
| 1861 | 2,118,000 |
| 1862 | 3,056,000 |
| 1863 | 2,631,000 |
| 1864 | 2,116,000 |
| 1865 | 2,497,000 |
| 1866 | 3,597,000 |
| 1867 | 3,347,000 |
| 1868 | 3,583,660 |
| 1869 | 4,210,720 |
| 1870 | 5,673,195 |
| 1871 | 5,715,900 |
| 1872 | 6,531,675 |
| 1873 | 9,884,719 |
The average daily product of this region from the discovery of petroleum to Jan. 1, 1874, is 10,852 bbls. The total product for the same time is 55,461,319 bbls. During the year 1873, 379,634 bbls. of crude oil was exported from New York city, the product of the Pennsylvania wells.
PETROLEUM PRODUCTS. The manufacture of commercial products from petroleum dates from the discovery of the crude material in large quantities in Pennsylvania. From the time the wells of that region first attracted at-
