Where the Word, Tarmac Comes From

The strange thing about the word 'tarmac' is that it is now associated with airports, as an area where planes are parked or are loaded, and most modern 'tarmacs' at airports are actually concrete.

I love this part:

> A workman could check the stone size himself by seeing if the stone would fit into his mouth.

They're probably laying down over a million stones per mile. Do all of them have to pass through a workman's mouth?