| http://www.w3.org/ns/prov#value | - ollowing detailed description, reference being had to the accompanying drawings, in which: Fig. 1 is an elevation, partlyin a broken away section, of a control head embodying my invention, also showing one means of attachment of the device to a well casing; Fig. 2 is a top elevation of Fig. 1; Fig. 3 is an enlarged section, partly in elevation, on line 3--3 of Fig. 2, the drill pipe, casing, and s
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