熱する: to heat

鉄てつを高温こうおんで熱ねっする。

Heat the iron at a high temperature.

シカやイノシシの骨ほねを火ひで熱ねっして、ひびの入はいり方かたを見みる占うらないです。

It was a kind of fortune-telling in which the bones of deer or boar were heated in a fire and the way the cracks formed was observed.