two to five beds of rock salt, 74 to 168 feet thick, lying 1,950 to 2,500 feet below the surface. Salt was first discovered in Cleveland in the Newburg district about 1886, when the Cleveland Rolling Mill Co., now the American Steel & Wire Co., was drilling for natural gas," "rock salt and shale" being penetrated between 1,990 and 2,154 feet and rock sait between 2,250 and 2,300 feet. The record shows three beds, 50, 20, and 5 feet thick, in addition to the 164-foot bed just mentioned. In conformity with the usual order of precipitation from saline solutions, all the salt beds are underlain by anhydrite, which the drillers termed "shale."

The first salt plant in the region was that of the Newburg Salt Co., which was started in 1889 and was last operated by the United Salt Co. Two wells were drilled in Mill Creek Valley south of Harvard Road, and brine was also piped to the plant from the original well of the Cleveland Rolling Mill Co. The plant was operated until 1902 but was dismantled in 1905.

The plant of the Cleveland Salt Co., at the corner of Ashland Road and Central Avenue, 4 miles north of the site occupied by the Newburg Salt Co., draws its brines from four wells on the premises. The first of the following records is that of well No. 2, which was finished November 4, 1905, and the second is that cited by Bownocker and called well No. 2 but now known as well No. 4. The two wells are not more than 500 feet apart. The "limestone" beneath each salt bed is probably anhydrite.

Record of well No. 2 of the Cleveland Salt Co.

16

The plant of the Union Salt Co., about 2 miles north of the Cleveland Salt Co.'s wells, at Addison Road and the New York Central Railroad, draws its brines from three wells on the property and two others a short distance away. The wells range in depth from 1,980

18 Ohio Geol. Survey, vol. 6, p. 352, 1888.

16 Bownocker, J. A., Ohio Geol. Survey Bull. 8, p. 36, 1906.

to 2,006.5 feet. The No. 2 well, the record of which, with interpretation, follows, has been abandoned. The No. 4 well, the record of which also is given, was drilled in 1893.

Record of No. 2 well of the Union Salt Co., Wason Street

Record of No. 4 well of the Union Salt Co., Hoyt Avenue

The No. 2 well penetrates a total of 159 feet of rock salt, if the 59 feet of mixed salt and limestone is omitted. The No. 4 well penetrates a total of 168 feet of salt, which, however, includes some of the strata omitted from the estimate for the No. 2 well. Though comparison of the records indicates a difference in the thickness and possibly in the number of salt beds within a distance of only a few hundred feet, part of the apparent discrepancies are doubtless due to imperfections in the driller's records. Comparison of these records with those of the wells of the Cleveland Salt Co. reveals similar apparent differences in composition and thickness of the beds at the distance of 2 miles that separates the plants. The No. 4 well of the Union Salt Co. is plugged at the bottom of the 59-foot bed of salt. The Cleveland Salt Co. stops drilling at the bottom of the first thick bed, which has a thickness of 64 to 72 feet. At the site of the Union Salt Co. this bed is 59 to 71 feet thick. Evidently there is about 74 feet of salt that is not tapped by the wells of the Cleveland Salt Co.

The salt is raised by pumping into the wells fresh water, which becomes a saturated artificial brine and is forced to the surface by additional pumping. Commercial grades of salt are manufactured at Cleveland from the artificial brine by both the vacuum-pan and the grainer process. Dairy and table salt are made, but the largest part of the product is made by the vacuum-pan method and is sold as No. 1 common fine, which is shipped loose and is loaded on cars direct from the curing floor.

NATURAL GAS AND PETROLEUM

Two general modes of occurrence of natural gas are usually distinguished. Gas is found in shale and is called shale gas; it occurs also in sandstone, conglomerate, and dolomitic limestone, and this is known as rock gas. Both types are recognizable in the Cleveland district, and a third type is also present, which might be called drift gas.

DRIFT GAS

The drift gas is the least abundant in the area and exists only in pockets in glacial clay or in layers of sand and gravel that lie between beds of such clay. Possible sources of this gas are the decomposition of organic matter either in the glacial drift or in the Cleveland and underlying Devonian shales, from which it may ascend into the drift. At least three occurrences of drift gas can be mentioned. One is in well No. 4 of the Union Salt Co., at Addison Road and the New York Central Railroad, where there is 267 feet of drift. A flow of gas of considerable volume was reported at 150 feet, and flows of lesser volume were obtained at 242 and 306 feet. The two higher flows were in drift, and the third was found 39 feet down in the Cleveland and underlying Devonian shales. The second occurrence is in well No. 2 of the Cleveland Salt Co., at Ashland Road and Central Avenue SE., which penetrated 520 feet of drift. At 445 feet gas was encountered in sufficient quantity to lift the drilling tools and prevent further drilling for a short time. A second well was driven alongside the salt tube to tap the gas supply, which, however, was soon exhausted. Layers of sand and gravel in the drift undoubtedly served as the reservoir for the gas tapped by these wells. A third occurrence of drift gas was found on the property of the late Thomas H. White, 8218 Euclid Avenue, Cleveland, where a shale-gas well that is still in use was driven about 1890. At a depth of 125 feet a pocket of drift gas was encountered, which blew boulders out of the well. A second pipe was put down beside the shale-gas pipe, and the gas supply thus obtained was sufficient for lighting, cooking, and heating for two years.

SHALE GAS

Shale gas ranks second in value in this district, but it is used more on a small scale by individuals than in industry. On account of one of its characteristic features shale gas is sometimes called low-pressure gas. Other characteristics are that the pressure is variable; the volume is small; the occurrence is not limited to any definite horizon and in many places is independent of oil; and the flow is likely to persist for a long time and is not dependent to any great extent on the structure of the rocks. Several hundred gas wells in the Cleveland district draw their supply from the shales, which have a thickness of about 1,250 feet. The wells range in depth from 400 to 1,840 feet, but most of them are completed at about 800 feet. This practice indicates that all the wells pass through the Cleveland and Chagrin shales into the shale of Portage age, which has commonly been called Huron shale. Although the shale of Portage age seems to be the chief source, it is known that the entire thickness of the Chagrin and Cleveland shales contains small quantities of oil and gas. Lord 17 states that the black shales contain one-fifth of 1 per cent of petroleum and that an average thickness of 1,000 feet of shale would contain more than 10,000,000 barrels of petroleum to the square mile. However, the oil is present in such minute quantities and is so widely distributed that it can not be profitably extracted. It is possible that this oil by decomposition forms the gas and that the gas, being more volatile than oil, is able to work its way along bedding planes, cracks, joint planes, and pores, in which it finally accumulates in small quantities when further migration is arrested.

The flow from a single shale-gas well is commonly ample to furnish light for one or more houses for a long period. Some wells furnish sufficient gas for light the entire year and for fuel in the summer, and a few supply enough for light and heat throughout the year. Pressures in the region range from 3 to 135 pounds to the square inch, the high limit, however, being exceptional. A well is considered good if the initial pressure is above 50 pounds and if it produces 50,000 cubic feet of gas daily. The daily open flow is generally less than 20,000 cubic feet, but the wells are comparatively long lived, some of them producing for 20 years or more. Near Lake Erie, especially west of the Cuyahoga River, a well driven to a depth of 800 feet is generally successful in finding gas. The writer's list of wells shows that more lie west of the Cuyahoga than east of it, especially along the lake. Near Berea many farmers have one or more wells, which furnish light and in some places heat. In that neighborhood the writer knows of no unsuccessful wells, but in Parma and Brecksville Townships several wells ranging in depth from 800 to

7 Lord, N. W., Ohio Geol. Survey, vol. 6, p. 413, 1888.

1,329 feet were drilled without striking gas. In the southern townships east of the Cuyahoga River, including Bedford, Northfield, and Boston, there are also successful wells about 800 feet deep. In the southern tier of townships west of the Cuyahoga River, however, including Columbia, Strongsville, Royalton, Brecksville, and the northern townships of Medina and Summit Counties, the number of gas wells is much smaller. The wells are also much deeper, owing to the southeasterly dip of the rocks, some being 1,200 to 1,300 feet deep, and gas is not always obtained. Royalton Township has two successful wells that are only 228 and 397 feet deep. The shallower well yields sufficient gas to light and heat one house all the year. It is believed that the gas originates in the Meadville or the Orangeville shale, or possibly in the Berea sandstone, rather than in the Cleveland and underlying Devonian shales.

The oldest shale-gas well in the Berea quadrangle, if not in the district, is in Rockport Township and was drilled in 1883 for H. A. Mastick.18 This well, which is still in use, is 527 feet deep and when opened yielded 21,643 cubic feet of gas daily.

ROCK GAS

Rock gas is generally a high-pressure gas and occurs in large volume at a definite horizon. Oil may or may not be associated with rock gas, and in most regions in which it is found the geologic structure is of great significance. Gas of this type occurs in all large fields, such as those of West Virginia, which have been furnishing the entire supply for Cleveland until the recent discovery of local gas at great depths in commercial amounts. In the Cleveland district rock gas, which is deep seated, was first developed about 1912 and is the most valuable natural gas in the region.

HISTORICAL NOTES

The oldest well in the district that produces rock gas was drilled in 1886, in Newburg, for the corporation then known as the Cleveland Rolling Mill Co. It has already been mentioned in the section on salt. This well was 3,000 feet deep and was thought to have reached the Trenton horizon. Two "sands" showing small amounts of oil were recorded in the Niagara limestone at depths of 2,658 and 2,686 feet. This is about the horizon of the so-called Newburg sand, which recent drilling operations have proved to be of some value as a source of gas and oil. The rock pressure was reported to be 400 to 500 pounds to the square inch, but the volume was only 14,000 to 16,000 cubic feet daily.

The discovery of gas and oil in Clinton (?) rocks in central Ohio between 1900 and 1907 proved an incentive to the continuation of 1 Ohio Geol. Survey, vol. 6, p. 432, 1888.