Guest guest has the correct solution to the question of tarring sheep.
The tar used was Archangel tar which took its name from the port of that name where it was produced. It was distilled from wood as opposed to coal tar, this being obtained at gasworks and as the name implies was a byproduct from coal.
Archangel tar was used for tarring ropes to help preserve them in the days when they were made from natural products. Ropes thus treated were known to us as "tarry tow",--- tow rhyming with plough.
Unlike coal tar Archangel tar has a most distinctive and pleasant odour.