The welkin, otherwise known as the loftsea, is the sea of wind that besets the earth.
The welkin is made up of 78 hundredths Stickstuff, and 21 hundredths Sourstuff. The scant other hundredth is a mix of idlestuff, airsteam, and wortloft. Of all known tungles, only Earth has a breathworthy welkin. The loftseas of other tungles lack the sourstuff to uphold the life of men and other wights.
The welkin has five layers: the bottomost, and the only one in which men can live, is the whirlingshoal. The second is the spreadshoal, the third is the middleshoal, the fourth is the searingshoal, and the fifth is the yondershoal.