228 INQUIRY INTO THE STRENGTH AND 
The results obtained from the preceeding ex- 
periments on the English irons, seem to furnish 
the best evidence that can be procured on the 
strength andother qualities investigated in this 
enquiry. 
On examination it will be found that conside- 
rable differences exist between one iron and 
another, but not more than the nature of the 
ores and their products wouldindicate. During 
the smelting process, the same qualities of iron 
are not always produced, as the Nos. 1, 2, and 3, 
and sometimes No. 4, are obtained from the 
same ores. M. Dufrenoy in his report to the 
Directors General of the mines of France, on the 
use of hot air in the Iron works of this country, 
states, “ that the iron obtained from a furnace 
is generally a mixture of No. 1 and No. 2; that 
which first issues from the hearthis No.1. The 
two sorts of pigs are known by the manner in 
which they flow, and above all by the disposi- 
tion of the streaks which mark the surface of 
the metal as it cools.” 
In addition to No. 1 and No. 2 mentioned by 
M. Dufrenoy, No. 3 is frequently produced ; it 
generally contains less carbon than No. 1 or 
