almost any metal."

"What is the best metal to harden steel?"

"Manganese, of which you will remember we have some samples; it is the most serviceable, as we have neither nickel nor chromium."

"What amount of that metal should we use to get the best results?"

"About 14 per cent. of manganese has been found the best for such purposes as would be required in gun barrels. There is a curious thing which has been discovered in uniting manganese with steel. It becomes fairly tough if 1 per cent. is used with the steel; if the quantity added is between 1-1/4 and 3-1/2 the strength and ductility decrease; but above that, up to 5 per cent., the steel becomes brittle; above 6-1/2 per cent. it again returns to ductility and toughness and its maximum strength is found at 14 per cent."

During the evenings all took a hand at cutting out the stocks for the guns, and the plans upon which they were constructed will be fully explained and illustrated in the order of the work done.

Meanwhile it must not be supposed that work on the new boat had ceased. Harry's plan, when fully worked out, provided for one twenty feet long and six and a half feet wide amidships.

The drawing (Fig. 2) shows the construction of the hull. As they had no means for doing any fancy bending of the boards, the bottom was made flat, and the sides sloping. The bottom and the sides were made in the following manner: Two stringers (A, A) were first constructed, which were made up of thin pieces nailed together, so they could be bent in the proper shape for the bottom boards, which were laid crosswise and nailed to these stringers.