SUPPLEMENT.

THE following comparisons of the dimensions of different reverberatory furnaces, and the conclusions to be drawn from

Reverberatory furnace for re-melting iron 100 1.6 1.6

Reverberatory furnace for heating iron

plates

Puddling furnace

0.50 2.00 1'00 2.6

2.6

4'5 5-4 13

ΙΟ

3'123'4

ΙΟ

1'7

1.3

do.

at Belgium

ΙΟ

1'4

3°2

4'48 2.8

0.87 2'3

1'12 I'45 I'12 3:18

3'55 2.5

Ι'Ο 2.8

0.8 13 1'04 13-0.5 2.1

2.31

2.2

0.89 1.9

0.78 0.33 0.60 0.30

ΙΟ 10-05 15

1'5

1'5

I

1'5

0'5

0'4

-

The following conclusions may be drawn from this table :a. If the surface of the grate is the same, the surface of the hearth is modified according to the heat which is to be produced, and consequently the hearths of roasting furnaces are two or three times larger than those of smelting furnaces; and the latter are again one-and-a-half times larger than those of puddling furnaces. In the same process the proportion of the hearth to the grate may vary from 10 to 4'1, but such large differences have a considerable influence upon the process, as is shown by the following table :

It follows from this that in England more substance is treated on 1 m, hearth in one hour with a smaller consumption of fuel, but with more labour, as it is oftener necessary to rearrange the melting mass on the larger hearth, which is less uniformly heated on account of its size.

b. The length of the grate is usually equal to the breadth of the hearth, which is from 1 to 2'5 times as long as it is broad. The height of the arch above the hearth is o'6 to 1 metre, and above the fire-bridge 0'3 metre. Upon one square decimetre of the surface of the grate o'5 to I kilos. of coal and I to 15 kilos. of wood, or respectively 0 ̊5—1 and 2.8—4°2 cubic decimetres are burned in one hour. In the lead furnace at Engis, for instance, 1000 kilos. of ore consume 650 kilos. of coal, and 0'45 kilo. of coal correspond with o'66 square decimetre of the surface of the grate.(Havrez in Revue Universelle, 6 an. 3 livr., 1862, p. 405.)

INDICES.

CLASSIFIED INDEX

SMELTING WORKS AND MINING DISTRICTS.