SALT AND COAL IN THE TEES DISTRICT. 489 



On resuming the boring, the Magnesian Limestone proved to be the 

 thinnest complete section in Durham, namely 299 feet; it was also 

 noticeable for the large proportion of gypsum and anhydrite con- 

 tained therein (see Appendix, p. 493). In boring bed No. 73 a 

 small feeder of brine was cut, as is often the case when drainage 

 from the salt-rock above — perhaps several miles away — flowing 

 through the underlying beds is tapped, and liberated by pumping. 



On analysis it was found to be a weak 6 °/o solution, of no 

 commercial value, though it continued to flow so long as the pumps 

 were kept going. A little later petroleum welled up continuously 

 as a black liquid ; and in addition to this, early in July, when the 

 boring went through the beds of bituminous shale with ironstone 

 nodules, IS'os. 88 to 90, the amount of hydrogen sulphide that was 

 set free was quite overpowering. 



The presence of bitumen, rock-oil, inflammable gases, or hydrogen 

 sulphide in the beds below the salt is often assumed to indicate 

 underlying Coal Measures from which they are supposed to be 

 derived. But this inference has proved erroneous again and again 

 on Tees-side, where the possibility of obtaining petroleum and 

 natural gas in paying quantities has been repeatedly discussed in 

 commercial circles.^ 



The nearest coal-workings to this borehole are Eodridge Colliery, 

 South Wingate, 7^ miles due north, and Bishop Middleham CoUiery, 

 about 7f miles north-west. Prof. Hull adopts, as the southern 

 margin of the Durham Coal-basin, a line which Sir Andrew Eamsay ^ 

 considered might be drawn from Seaton Carew westward to Midd- 

 ridge Grange. " To the south of this line, the Permian and Triassic 

 strata would be found to overlie only Millstone Grit and Yoredale 

 rocks." '^ 



A boring near Spiceley, half a mile south-east of Bishop Mid- 

 dleham Colliery, after passing through 284 feet of surface -deposits 

 and Magnesian Limestone, struck Millstone Grits which were 

 followed for 107 feet. Discussing its bearings on the Coal-area, 

 Sir Lowthian Bell suggested that " an anticlinal axis might, how- 

 ever, restore the coal under the Magnesian Limestone."^ At 

 Bradbury Carr a borehole penetrated surface-drift 125 feet thick, 

 Magnesian Limestone 200 feet, and Yoredale Eocks 225 feet. The 

 nearest borehole to this is at Elstob, 5| miles west of Whitehouse : 

 thickness of surface-deposits 125 feet, Magnesian Limestone 225 feet, 

 Yoredales 550 feet.' 



The Seaton Carew boring reported by Mr. "Wilson down to 1761 

 feet, August 16th, 1888, was finally abandoned in the October 

 following, at a depth of 1815 feet, having added 54 feet of grey 



i ' Colliery Guardian ' for 1891, p. 523 ; ' Northern Echo,' March, 1890. 



2 Eamsay, Eep. E. Coal Commission (1870), p. 139 ; based upon evidence 

 supplied by Mr. H. H. Howell. 



3 ' Coal- Fields of Great Britain,' 3rd ed. p. 254. 



4 Proo. Inst. Civ. Eng. rol. xc. (1887) p. 133. 



5 Geol. Surv., Horizontal Section, Sheet 133, and Vertical, Sheet 65. The 

 writer has to thank Mr. H. H. Howell, of the Geol, Survey, for kindly directing 

 his attention to this information. 



