IRON SHIPBUILDING.

963

ships, to the new material, mild Steel; it also shows that by far thegreater number of vessels now building are ships of large dimensionspropelled by engine power:—

Mild Steel Iron. Wood. Total.

No. Tons gross. No. Tons gross. No. Tons gross. No. Tons gross.

Steam,. 89 ... 159,751 555 ... 929,921 6 ... 460 650 ... 1,090,132

Sailing,. 11 ... 16,800 70... 120,259 49 ...4635 130... 141,694

100 ... 176,551 625...1,050,180 55 ... 5095 780 ... 1,232,826

If to the improvements already achieved could be added an engineof half the weight of the present steam engine and boilers, andworking with only half the present expenditure of fuel, a furtheraddition of 30 per cent. could be made to the cargo of an Atlanticpropeller vessel—no longer to be called a steamer—and the balanceof advantages in favour of such vessels would be sufficient to restrictthe use of sailing craft chiefly to the regattas of this and neighbour-ing ports.”

As it is important to have the rust removed from all metal workbefore painting, so it has been found that for Steel plates it is ofimportance to have the mill scale removed by some more com-plete process than hammering. This is accomplished by placingthe plates in a bath of dilute hydrochloric acid, where they are keptfor four or five hours.

The following results of experiments on the corrosion of Steeland iron plates have been submitted recently in a paper by Mr.Farquharson, read before the Institution of Naval Architects. Theplates were treated with dilute hydrochloric acid, and the loss ofeach plate noted as follows:—

Steel

combined, .

oz.grs.

10-427

Steel,.

oz.grs.

4-0

Iron

1 7'417

Iron,.

3 -I 9°

Steel,

3'340

l 2 '337

Iron,

3'3 2 7

Iron )

l 6'o

Steel

combined, . . .

1 0-297

Steel,.

4'i57

iron )

l 777

Iron,.

4'57

The loss of the separate plates of Steel and of iron appears prettymuch the same, but it is very noticeable that in the combined platesa greater loss takes place in the iron plate, showing that electricalaction has been set up. This is of considerable importance whenwe consider that in some cases iron rivets are used for fasteningSteel plates.

The following table gives the weight of iron, Steel, and othermetals for these volumes—i cubic foot; 1 square foot 1 inch thick,