kept firm and tight in their holders to make a good contact. All bolts and
nuts fastening the electrical contacts should be clean and tight at all
times.

The scale may be removed from forgings by immersing them in a pickling
solution in a wood, stone or lead-lined tank.

The solution is made with five gallons of commercial sulphuric acid in
150 gallons of water. To get the quickest and best results from this
method, the solution should be kept as near the boiling point as possible
by having a coil of extra heavy lead pipe running inside the tank and
carrying live steam. A very few minutes in this bath will remove the scale
and the parts should then be washed in running water. After this washing
they should be dipped into a bath of 50 pounds of unslaked lime in 150
gallons of water to neutralize any trace of acid.

Cast iron cannot be commercially welded, as it is high in carbon and
silicon, and passes suddenly from a crystalline to a fluid state when
brought to the welding temperature. With steel or wrought iron the
temperature must be kept below the melting point to avoid injury to the
metal. The metal must be heated quickly and pressed together with
sufficient force to push all burnt metal out of the joint.

High carbon steel can be welded, but must be annealed after welding to
overcome the strains set up by the heat being applied at one place. Good
results are hard to obtain when the carbon runs as high as 75 points, and
steel of this class can only be handled by an experienced operator. If the
steel is below 25 points in carbon content, good welds will always be the
result. To weld high carbon to low carbon steel, the stock should be
clamped in the dies with the low carbon stock sticking considerably further