to fig1 the temperature differential of approximately 1400 u00b0 f to 650 u00b0 f across condenser 1 this establishes a negative pressure in view of the fact that liquid products are recovered from the unit the same is true with condenser 2 which goes from approximately 650 u00b0 f to 250 u00b0 and then another 200 u00b0 180 u00b0 temperature differential before the output goes to condenser number three oil shale is present in various strata with significant horizontal permeability and very little vertical permeability the horizontal permeability of one layer might be quite different from the permeability of other layers the use of compressor 216 in conjunction with pressure differentials across the condensers establishes a negative pressure all the way down into the well as vapor molecules leaving the well are pulled across the face of the rock a venturi effect is created that effectively draws the now heated kerogen out of these horizontally permeable strata this action improves extraction facilitating an active rather than passive collection of products the combination of various physical parameters associated with the invention allows for a wide range of adjustments in overall operation as one example assume that the system is producing an undesirable high percentage of heavy crude several things may be done to rectify such a situation excess.