The generator should now be charged with carbide, but before doing so it is very important to read carefully the maker's printed instructions, and study the Regulations and Precautions given on page 84.

Before starting up it is necessary to read and carefullv observe the notes and instructions on page 90.

The Complete Apparatus is now ready for use.

We are now ready to start welding, and the first thing to do is :-

1. ;Adjust the oxygen regulator to the correct pressure. We may now-

2. ;Light the blowpipe.

To do this open the oxygen valve B on the blowpipe, turn on the acetylene tap fully and apply a light to the nozzle. At first a brilliant white flame will appear. This denotes an excess of acetylene, and the flame must be reduced by gradually closing the acetylene tap C until a well defined white cone appears at the blowpipe nozzle. The length of this cone varies from about 1/8 of an inch to 3/4 of an inch, according to the size of the blowpipe employed, and should be as large as possible for the nozzle in use, with a sharply defined outline. (See Fig. 221.)

When the weld has been completed or when it is desired to stop, the acetylene tap on the blowpipe must be closed first and then the oxygen valve. When work is completely stopped the oxygen cylinder must also be shut off, and the pressure released from the regulator. The acetylene tap B on the hydraulic back pressure valve should also be closed. Always shut the cylinder valve when the cylinder is empty or not in use.