LOCAL SURFACE AND UNDEEGROUND SPRINGS. 173 



18 in. cores in connection with a bore-hole I put down (for 

 my Company) at Chelvey, on the Keuper Marls, New Red 

 Sandstone, and Dolomitic conglomerate, samples of which 

 I have here. In this case the hole was commenced 160 feet 

 below surface (the surface being 50 feet below sea level), or 

 say 100 feet below sea level where the boring was com- 

 menced, and, as the section shows, to a depth of 400 feet. 

 The larger bulk of water was met with in the Sandstone, 

 about 200 feet from surface, and other small quantities at 

 depths of 230-290 feet. The passage from the Keuper 

 Sandstone to the Dolomitic is very clearly marked, and the 

 Dolomitic proved to be about 30 feet thick when the blue 

 duns of the coal measures were reached, which shows that 

 we were near the outcrop of the Nailsea Coal Basin. Here 

 the boring was stopped, and I may remark that the 

 additional yield due to this hole was afterwards proved 

 by pumping to be about a million gallons. 



It may be interesting to the Society to explain here the 

 mode of boring these holes. It is done with a diamond 

 crown (that is black diamonds set in a steel coronet), 

 which is attached to screwed tubes and rotated by engine 

 power and suitable gear from the surface by connecting 

 rods and tubes. A core like the sample is cut out and 

 withdrawn as required. 



The means of withdrawing and holding the core is also 

 interesting ; the core is pressed up into a tube about 15 

 or 20 feet in length. About two-thirds up its length it 

 has a diaphragm, which, as the rotation goes on, allows the 

 debris to pass the sides of the core by an annular space 

 and become deposited in the top shelf of the tube. When 

 the core is of such a length that it requires drawing, or 

 should it break off, it is secured by a split ring tightening 

 in an inverted cone, which, by the action of lifting the 



