Because they're robots in disguise.
There is 2 shafts in a coal mine.
safety
down
they are also known as pies or infections
Spawners are found in dungeons and mine shafts.
(I take it you are referring to the abandoned mine shafts.) The mine shafts were added to the PC version at the 1.8 update. The Xbox version is at 1.6.6, so you can't find any.
an air velocity meter to measure the speed of ventilating air in mine shafts
you just randomly click
an air velocity meter to measure the speed of ventilating air in mine shafts
it goes deeper into the earth and gets hotter.
Vertical or inclined shafts are typically dug to reach deep mines. These shafts are large, circular excavations that provide access to the underground workings of the mine. They allow miners, equipment, and mined materials to be transported in and out of the mine.
The Greeks and Romans were using them 2500 to 3000 years ago to pump out mine shafts.