The Hobbit, Chapter IX, Barrels Out of Bond, p. 163Balin was told off to watch the guard and the butler and give warning if they stirred. The rest went into the adjoining cellar with the trapdoors. There was little time to lose. Before long, as Bilbo knew, some elves were under orders to come down and help the butler get the empty barrels through the doors into the stream. These were in fact already standing in rows in the middle of the floor waiting to be pushed off.
The Hobbit, Chapter IX, Barrels Out of Bond, p. 166....Leave the northern mountains steep,.....
The Hobbit, Chapter IX, Barrels Out of Bond, p.167- for you cannot count friends that are all packed up in barrels
The Hobbit, Chapter XII, Inside Information, p. 193It was at this point that Bilbo stopped. Going on from there was the bravest thing he ever did. The tremendous things that happened afterwards were as nothing compared to it. He fought the real battle in the tunnel alone, before he ever saw the vast danger that lay in wait. At any rate after a short halt go on he did; and you can picture him coming to the end of the tunnel, an opening of much the same size and shape as the door above. Through it peeps the hobbit's little head. Before him lies the great bottom-most cellar or dungeon-hall of the ancient dwarves right at the Mountain's root. It is almost dark so that its vastness can only be dimly guessed, but rising from the near side of the rocky floor there is a great glow. The glow of Smaug!
The Silmarillion, Of the Voyage of Eärendil and the War of WrathBefore the rising of the Eärendel slew Ancalagon the Black, the mightiest of the dragon-host...
The Silmarillion, Of the Return of the NoldorAgain after a hundred years Glaurung, the first of the Urulóki, the fire-drake of the north, issued from Angband's gates by night.
The Hobbit, An Unexpected PartyThere were lots of dragons in the North in those days... There was a most specially greedy, strong and wicked worm called Smaug.
The Lord of the Rings, The Return of the King, Many PArtings'It was made by the Dwarves, and came from the hoard of Scatha the Worm.'
Lord of hte Rings, Fellowship of the Ring, The Shadow of the PastThe conversation in The Green Dragon at Bywater...