Thierry Merlin was the first producer I started with, and he has been one of the most consistent. He works fourteen hectares of vines in Bu?, one of the principal hamlets surrounding the old walled town of Sancerre. That town, once a Protestant stronghold, was sacked in the 16th century and again in the 17th during the Wars of Religion. It was a stronghold because Sancerre commands the highest hill above the Loire River, rising above a landscape of hills on the east side of the river (the appellation of Pouilly-Fum? across the river has little of Sancerre's muscular hills and dales). Bu? occupies a small pocket canyon behind Sancerre, and the hills rising above this village on three sides are covered in vines. Bu?'s soils are composed of Sancerre's two main types: caillottes and terres blanches (the third important type is silex, or flint, and is restricted to a north-south fault line that runs right through the town of Sancerre). Caillottes, referring to stones, is a very stony, compact chalk without a lot of clay and marl. Geologically, caillottes is Oxfordian Limestone. It's generally found on the lower hills and in the middle north-south zone of the appellation, and it predominates in Bu?. This soil makes for perfumed, elegant wines. Terres blanches, or white earth (in dry periods, the seashell-rich soil turns white), is found on higher hills-it's a younger soil type than Oxfordian-and dominates in the western arc of the appellation. Terres blanches is limestone pebbles and rocks mixed with a good amount of clay marls on Kimmeridgian limestone. The technical term for terres blanches is Kimmeridgian Marl. This soil makes for pointedly fruity, rich, long-lived wines.