Some of the glass tubes recovered are fire - closed at one end .
Some of the glass tubes recovered are partially inflated by blowing through the open end while still hot to form a small bottle ; thus they are considered as a rudimentary form of blowpipe .
Some of the glass tubes recovered are fire - closed at one end and are partially inflated by blowing through the open end while still hot to form a small bottle ; thus they are considered as a rudimentary form of blowpipe .