in 1936, its predecessor in title leased the oil and gas underlying a large tract of land, "with the exclusive right of mining and operating thereon for the production of oil and gas", to the defendant Godfrey L. Cabot, Inc., hereinafter called Cabot, on a one-eighth royalty basis, pursuant to which Cabot drilled a number of wells into the Big Lime stratum, including two wells, Nos. 1060 and 1087, on a certain 795 acre portion of the leased tract. This 795 acres is now a part of defendant United Fuel Gas Company's Storage Pool X-1, and is included in an agreement entered into by Cabot in 1948 with United Fuel Gas Company, whereby Cabot granted, in so far as it had the right to do so, "the exclusiveCabot acquired the right to produce oil and gas from all strata under a 2,762.72 acre tract, of which the 795 acre tract involved in this litigation was a part; (2) an executory agreement of May 7, 1948, between Cabot and United Fuel Gas Company, hereafter referred to as United, Exhibit No. 3, by which United would subsequently acquire the right to utilize the Big Lime formation under a tract of 3,537.90 acres, of which the 795 acre tract was a part, provided that United should, within a specified time thereafter, secure the necessary additional rights from the owners of estates therein other than Cabot; (3) the agreement of April 28, 1949, between plaintiff's predecessor in title and United, Exhibit No. 4, whereby United secured certain rights in