Lime kiln Wikipedia
The common feature of early kilns was an eggcup shaped burning chamber, with an air inlet at the base (the quot;eyequot;), constructed of brick. Limestone was crushed (often by hand) to fairly uniform 2060 mm (1 2 1 2 in) lumps fine stone was rejected. Successive domeshaped layers of limestone and wood or coal were built up in the kiln on grate bars across the eye.