Looking at this, it occurred to me that something was wrong here. Then I twigged it.
The way he's drawn the shadows, the 'Entrance' is on the west of the circle - where the quartz stone is. Would this have been the entrance? Everything today point sto the entrance being opposit ethis stone, where the gate is now, at the end of the track to the farm.
Is this just another example of Stukeley's inconsistency and artistic license?