'Shade' in the Bible

And Isaiah said, This is the sign the Lord will give you, that he will do what he has said; will the shade go forward ten degrees or back?

And Hezekiah said in answer, It is a simple thing for the shade to go forward; but let it go back ten degrees.

Then Isaiah the prophet made prayer to the Lord, and he made the shade go back ten degrees from its position on the steps of Ahaz.