76 
POPULAR SCIENCE REVIEW. 
must be closely attended to. In Germany, a puddled steel, 
which is much in request, is prepared by a process analogous to 
the puddling of iron ; the only difference being, that as soon as a 
sufficient quantity of the carbon lias been removed, the access 
of air is prevented, and the carbonized metal is retained, without 
change, in a molten state for working. This puddled steel is 
not so much used for cutting-instruments, as for the steel orna- 
ments, and fancy articles which the Germans produce so largely, 
and for steel axles, winches, tires, &c. 
The Indian wootz is prepared from a very rich magnetic oxide 
of iron, by a rude process, differing indeed in no respect from 
that which the natives of India employed when Alexander 
marched into Asia with his conquering army. In the first 
place, a cake of brittle grey iron is produced, with considerable 
waste in the slag. Cakes are carefully selected, annealed for 
several hours in small charcoal furnaces, finally carefully re- 
melted, and cast into ingots. The finest ingots are taken and 
drawn out by a hammer of a few pounds’ weight. Thus the 
finest Indian sword-blades are manufactured. Damascus steel, 
which is principally worked up into sword-blades, consists of a 
more highly carburetted steel than any European manufacture ; 
and the peculiar characteristic Damascened patterns which 
appear on the steel, are due to a skilful cooling, by which a 
division is effected between two carburets of iron. The wonder- 
ful temper of the Indian and Damascus blades, which has been 
almost the despair of European cutlers, is due to the regulated 
temperature at which the blade is worked. If this be too high, 
the metal flies to pieces; if too low, it becomes hard and 
inflexible. The Indian steel has been cleverly imitated by 
combining nickel, manganese, and tungsten with the iron, and 
also by welding together plates of iron and steel. None of 
these imitations, however, possess all the peculiarities of the 
Damascus steel. 
Steel differs from wrought iron in possessing the remarkable 
property of becoming intensely hard, if, after having been made 
red hot, it is plunged into cold water. If the metal has been 
brought up to a melting heat, and then suddenly cooled, such 
'an arrangement of the particles takes place as to give the steel 
a hardness sufficient to scratch glass. By the process known 
as “ tempering,” almost any degree of softness can be obtained. 
In the entire range of metallurgy, there is no operation more 
deserving attentive study than this. The surface of the steel 
is polished, and it is exposed to heat. As the heat is increased, 
there is a curious and uniform change in the colour of the 
surface. The first visible tinge of yellow increases the tough- 
ness without diminishing the hardness ; a deep yellow or orange 
indicates that the condition is that which is fitted for razors or 
